I think the reports of drained battery life have a lot to do with people misconfiguring it. For one, there is no need to sync folders other than the inbox unless you filter mail to folders and leave them unread. If you do this, then syncing that folder will show you how many unread messages there are when you browse the folders. However, you will not get a badge on the Mail icon as that is only for the inbox. If you manually browse to any folder, the messages will be automatically downloaded. So, unless you need to see the unread count in the folder list, do not sync a lot of folders. Also, if you are setting up a bunch of folders and are setting it to sync a month or "no limit", then you will get a lot of a battery drain as it will take much longer to sync.