I've bought 'released' items from them without any issue - however they are part of "the hut group" http://en.wikipedia.org/wiki/The_Hut_Group which includes Zavvi who i have had 'delays' on pre-releases from.
Given that link I probably wouldn't go for anything you *want* to have on Day 1 (Like...
Tesco have it in store and online at £28 if you buy points or a 3 month subscription with it
Online link : http://www.tescoentertainment.com/store/browse/games/GearsOfWar3LaunchOffer/?utm_source=Home&utm_medium=Rotating1&utm_campaign=GearsOfWar3LaunchOffer
In store display :