When I started bow hunting a few years back I got a single pin at the behest of a professional archer I know. I was leery, but he was/is so knowledgeable he won me over. We agreed to give it a season. I loved the FOV available when I would draw back. I loved it so much I swapped out my Burris FF2 2-7 on my .30-06 and put a Leupold FX2 4x. And since then I have been paying more attention to the situation when I take deer - and two things continue to repeat themselves (until last night): 1) I have never had the time to change the power of my scope when a shooter comes by, and 2) the most magnification I have ever used in the woods here in TN was 4 or 5. (But, when I get an invite to hunt in Oklahoma or over fields I use my 7mm-08 which now uses the Burris.)
About last night - I have an old, Rimfire, 3-9x40, Cabela's branded scope on my muzzleloader. (I would have a fixed if I could justify another scope, and I rarely hunt w/ my muzzy.) Alas, I had an 8 hiding behind some small tree junk watching a couple of doe. I dialed the scope up to 9x to check points and size. That was a first to have the time to adjust my scope in a situation where I would consider pulling the trigger (and I did). But at 55 yards, the FOV is quite limited and it took me a while to re-scope the deer after dialing up the magnification. And the foliage didn't help. Could I have counted to 8 with a fixed 4x? Probably. At 3x I guessed it was an 8. And certainly better glass would have helped these tired eyes.
So, I'm a huge fan of fixed scopes. I've even talked with a Burris rep about reintroducing one. I don't think I would have ever gone this route if I hadn't gone with a single pin bow hunting. But around here and the way I hunt, I'm not going back.
$.02
edit - I also shoot the V2 Optima. Freaky accurate with 2 777's and Hornady 240g