For me it seemed to have problems syncing, forgot my password frequently, and just various other problems.
I tried it very early on and then again recently--my more recent issues were more than it is almost too busy when compared to Mail.app which gets the job done.
I couldn't say they fixed everything however as I didn't really spend too much time in it in my more recent experimenting with it.
It does create some Gmail labels/folders which can be a problem if you find that annoying--I have enough as it is haha.
