When I bought my Bengal in fall of '09, that was the first time I had tried a drop rest or release...AND...first time ever with a peep.
I shot fingers and used a sight without a peep since the brass pin days. (how have archery peep sights been around?)
My groups are tighter now, I assume mostly due to the release, but I can see where the peep helps especially if your form and/or anchor point gets slightly off.
FYI: speed tests I've done on my current bow showed about 2fps loss adding G5 Meta Peep, and I've seen only 1fps with cat whiskers on all three of our bows.
(can't remember the exact loss I had from the tube peep I had at first right now, but it was more than double the tubeless peep)
2009 Martin Bengal M2 Pro Cam w/factory STS & CCS.....66lbs, 29" DL, 422gr @ 272fps, Winners Choice string/cable, Trophy Taker drop-away Rest, Scott Release
1996 Martin Firecat XRG Pro Series w/Ultra Sonic wheels.....69lbs, 29" DL, 465gr @ 245fps, w/fingers & Martin leather glove