I downloaded it but it won't start up.. .it gets started, says wait a few minutes and then locks up... won't go anywhere. The phone is fine, just that gmail wont load... I had the same things with gmaps.
I also have TMobile 8320. I didn't have any trouble downloading and installing google. As jhill suggested, I already had my gmail registered with Tmo and and coming to my phone. I only installed gmail, google maps, and the google search page. I recommend deleting what you've got and trying again after a reset.
Posted from my CrackBerry at wapforums.crackberry.com