OK I have been able to get a full day from my Eris but use has been moderate. One day I did hit 15% warning by the end of the work day with alot of use but this weekend while exploring the phone some more I toyed with the setting for enable always-on mobile data (enabled by default) and un checked it. I still get my gmail as I did before but the battery seems to last alot longer. Not sure on Facebook updates but I have it set to send me email for posts on my wall anyway so no biggie. Played Bonsai Blast, some texting, Facebook posts and a couple calls today and I am still above 50% at 10PM. I will leave it on overnight and follow up tomorrow to let you know. To get to this setting go to settings>Wireless controls>Mobile network settings>Enable always-on mobile data (uncheck) give it a try and see if it helps. Not sure if this effects exchange or pop/imap email services or not. Sorry if this is repeated anywhere else.