I shoot a variety of shotguns, some with scopes and some without. I've tried a lot of fiber optic sights over the years, some good, some not so good.
I've also tried a whole series of red/green dot sights, that range from the first generation Bushnell Holo sight up to some of the more modern variable reticle "dot" sights. I know that a lot of folks really like them and I've used some for several seasons but they are just not for me, when I hunt.
I also have shot/shoot a variety of telescopic sights on my shotguns. I use them for still target shooting, card shooting, etc. and really like them for that. I shoot several Leupolds and a variety of others. I really think some of the best bargains today come from Simmons (the fixed 4 power diamond reticle) and some of the BSA scopes.
For turkey hunting, I usually just use beads. Since last September I've been shooting a Winchester SX3 as much as possible, fall and spring turkey hunts included. It's light, quick and fits me as well as any gun I shoot.
A scope can have an advantage, in my opinion, if it allows you to better judge distance. The diamond reticle scope is an example. It has a built in "range finder". To me the disadvantage of any scope is added weight and they can make a gun top heavy and keep it from balancing in your hand.
The sight that intrigues me most is the new Burris Speed Bead sight. If you've not looked at that one, you can find it here: http://www.swfa.com/c-2178-burris-speed ... stems.aspx
That's a very light sight that would not effect the balance of your gun (if they make one for yours) and has several advantages over some others, due to the way it mounts to the gun.
Hope that helps some.