I just saw it and thought that it was okay & not particularly harmful to sorority life. I didn't really see a Zeta Tau Alpha and Zeta Alpha Zeta similarity. The Zeta letters on the front of the house were kind of a teal'y blue (which is also a ZTA colour) and that was about it. The mean, bitchy sorority house on campus was called "Phi Iota Mu", so I suppose Phi Mu could make a case that that was a bit close to their letters and they don't like the way in which it's represented.
Anyhow, it was a pretty good movie. In the end, the message was essentially, "be yourself, but be your best self" (whereas in GREASE, which is another extremely popular movie and musical, Sandy completely sells out in the end).
There were a few inaccuracies, like them mailing out the bid cards, and in the end, one girl from Phi Iota Mu wants to join Zeta Alpha Zeta (and of course, you can't really do that if you've already initiated in NPC land...and I'm sure locals would not look that kindly upon it either) and then of course, the Aztec party with alcohol served at a sorority house (hello, Risk Management). But that's me just over analyzing it and it is just a movie!
P.S. Beverly D'Angelo was great...so awesome as the House Mother of the Phi Iota Mu.