I guess that I am old fashioned, but I have been using the tried and true Fletcher Super Hunter for years. I refuse to ever use one with a tube, and with a good string to stop twisting, I have never had a problem with it not lining up. I did just look at the Whisper Peep Liteby Loc A Peep and am impressed. The Lite version doesn't use the tube. Check out their website at www.locapeep.com
I might just check one out sometime, but I honestly love the Super Hunter.