There has been some great debate in this discussion topic. To stay focused on gear specific material there is a lot to consider in sights and optics for any firearm. The fist thing to keep in mind is "does it do the job the way it is?" The answer is probably yes, since all you are really doing is pointing the barrel in the bird's direction, and sending a bunch of pellets down a tube that open into a cone, and hopefully, if things go as planned, take down the turkey.
I have been considering a scope for about three years for my turkey gun. It came with fibre optic rifle sights which illuminate great in low or high light situations. If you prefer a standard single or double steel bead, then congratulations, you are set to go with a standard, simple set up. However, if you are looking for something more, then you have a lot of options. There are fibre optic sights, red dot sights, and scopes. Inside of those three categories there are even more options to consider. I would take an overall look at your current gun's setup, or the gun you are considering using/buying. If you currently have a simple gun, such as a Remington 870 Express then you will have to consider many things. For example, if you run out, buy a B-Square mount, and toss on a scope, you will probably not be doing yourself a favour. The standard straight comb stock does not allow for proper or good eye alignment. A B-Square mound does however allow for you to see the bead underneath of the scope mount (a sort of see-through mount). Unless you feel like getting a raised comb stock, and changing your setup completely, I would suggest starting with or trying a simple set of sights that attach to a vent rib barrel. Try, or at least take a look at Sight Science Turkey Buster Sights, HiViz TriViz Turkey Sights, HiViz Tom Buster II, or TruGlo Tru-Bead Turkey Globe Sights, or something similar. The reason I listed these sights is because they mount low to the barrel, that way you will get a better sight to eye alignment with a straight comb stock. There are dozens of other great reasons to stick with simple sights.
Your next option is a red dot sight. I used a simple, cheap, red dot sight for a while just to get an idea of what it would be like. I was not a big fan of the idea that it used batteries, among other reasons. I had nightmares (not actually) that when the shot presented itself that my batteries would be dead. Also, unless you want to sit there with it turned on the whole time, you have to reach up and turn it on when the shot presents itself. So now you have two buttons to push, the safety, and the on button for your red dot. I am not saying that this is the worst choice, but I felt it was too risky and not for me. Pros for red dot sights are that they range in price from low to high. They have multiple reticles to choose from, some of them even have multiple retackles in one sight. Not only do they come in red dot, but also green dot, depending on what you prefer. They are lighter than scopes. They stay with a 1 x power, so magnification is not an issue. They allow for more certain shot placement (if you use a crosshair reticle or alike). There are even a couple of red dot sights on the market now that have magnification. One such sight/scope is made by TRUGLO and is a fixed 2x red and green multi reticle.
Now onto the original discussion topic, scopes. The question asked "yes or no?" My response is "sure, if you want to try one." I have been looking at a few scopes and considering them for myself. I've actually been taking a long time to think it over (three years. It took me less time to ask my wife to marry me than it has to pick a scope). As mentioned in a previous post by another hunter, keep in mind eye relief. Those 3 ½" magnum loads put out a lot of recoil, and if you are not aware of it, you may likely end up with a scope bight. I have had it happen at the range a couple of times (luckily I was wearing safety glasses and did not get injured). I have tried a couple of scopes to date. Since I use a Remington 870, and I did not want to drill and tap my receiver, I tried a B-Square shotgun scope mount combo. Forget the scope combo, I found the scope that came with it to be to cheap and flimsy, and it did not hold up. When adjusting the windage, I actually was able to break the adjustment screw. A shame since it has a 6" eye relief. The mount itself is good, and is available for a small, but growing variety of makes and models.
I have a Nikon SlugHunter shotgun scope for my cantilever deer barrel. This is a great shotgun specific scope. However it is a 3-9 power, and has too much magnification for turkeys. I tired it on the B-square mount, and I found it fit well and had a good feel and balance to it. Keep in mind that with the mount, the scope, the rings, ammo in it, and a Hunters' Specialties mono/bipod (I use one of these because it keeps my gun in a ready position and allows for more steady aimed shots), you may be lugging a 10 - 12 pound turkey taming piece of hardware around. If you are looking for a place to start, I would take a look at the RedHead Accent Shotgun Scope (1.5-4.5x32), the Nikon ProStaff Shotgun Scope (2-7x32), or the Bushnell Trophy Shotgun Scope (1.75-4x32). I have looked at all three and of the three I am now strongly considering the Bushnell Trophy. It has a circle cross reticle, which I felt would be ideal for placing the turkey's head and neck in. It also has 4" of eye relief, and does not weigh as much as the other two. I felt that the RedHead accent was too heavy, and it was not as clear or as bright. The Nikon was good, but it had slightly less eye relief, and weighed a bit more. All three are around the same price, from $125 - $155.
I'd like to think that I am not an advocate of any one particular brand, but I will, and do mention particular brands often. That is simply because those are the products I have tried. Also consider the rings that you are putting on the scope. Will they hold up to the punishing that will come from 3 ½" magnum turkey loads? A final thought when considering a scope is the versatility of it. What I mean is, can you use that scope for more than one thing if you had or wanted to? I currently use a Nikon SlugHunter for my cantilever deer barrel, which has a 5" eye relief. If you do not have a shotgun scope or mount yet, and you were looking at one of the three above that I suggested, then consider the following. What sort of mount do you want to put on the gun? Do you want to drill and tap it and put a mount on it? Or do you want a simple and easy to remove mount, such as the B-Square? Next, do you want to be able to use the scope for more than just turkey, such as deer, and other big game? You may want to consider a scope, mount, and barrel setup that will allow you more versatility. Since slug guns and turkey guns share some of the same features, why not carry find a cope that will suite both? The Bushnell Trophy for example has an ideal reticle and eye relief for both deer and turkey hunting. So why not get two uses for the price of one scope?
This is more of a reminder for me, but I felt I should share it with others. Be wary of the "gear head virus." It happens when you see, think about, search out, and then obsess over every new gun, gadget, and piece of gear on the market. I've had it before. The cure is to realize that your skills determine your success more than your gear does (not to mention your budget may be limiting). The old single bead may bring home more game than the scope. But it sure is nice to have the option isn't it?
I hope this information and input helped anyone who was looking for some direction on whether or not to go scoped or unscoped. Start out small and simple, and work your way up. It may take time, and it may cost money, but the results and satisfaction may be greater in the end.