Yes. Gears 3 was originally scheduled for release in the first few months of 2011. Microsoft delayed it until Sept. for the holiday sales block. They didn't announce the delay until it was near the original release date, so Epic had a near complete build
of the game in early 2011. So they could either sit on a complete version of the game for 6 months, or use that time to avoid a Gears 2 release disaster.
Pretty much what Storm and Skill said. 1) a beta isnt a demo, there are bound to be problems with a beta. We're so used to betas typically being a demo and when a real beta comes out, we all lose out cool because we have the mentality of hey, its a demo.
2) just like what storm said, GOW 3 was more than likely 95% complete by the time they released their "beta" since the release was pushed back. So rather than having a build like this, they had essentially a final version of the game they let people play
Gears was due out in Nov 2010, then Apr 2011 then Sep 2011. I am sure as each date got closer they had a close to finished project. Also remember that Gears is XBOX 360 only, BF3 on the other hand needs to be coded for PC/XBOX/PS3 all at the same time.
Don't get me wrong, I have real issues with this beta (demo really based on the time frame) but you can not compare it to Gears of War 3