I like the gmail web interface above anything else I've used. That's pretty much what I stick with.
I'm running two Gmail accounts through Mail right now (along with a MobileMe and a Hotmail account) and have had no issues whatsoever. What seems to be the "odd acting"? Maybe some more details would help.
If I am looking on the gmail website, it shows messages in the inbox. But, I go to the inbox in Mail, and the messages are not there.
Sometimes, a new message shows up and Mail shows a red circle with a number in it, but the message itself does not show (but it is clearly visible on the website).
MotionMan
It works fine here... I've been using it for almost 2 years now.. whenever they enabled IMAP. I use it on my Mac Pro, Macbook Pro, iPhone, and iPad. Make sure IMAP is enabled in gmail itself, its not by default.
Gmail + Exchange is where its at.
Set it up as an exchange server.