I've tried every solution under the sun and the best non-BES solution I've come up with is this.
If you need BIS to sync with your Google Apps email account, you need to talk to your provider and get a case number to call RIM. RIM will then set your domain up as a GMail domain. Chances are, your provider won't know what you're talking about, so you'll need to go through all the basic troubleshooting before they finally give up and refer you to RIM. Just be persistent. I guess you might be able to call RIM directly if you're willing to pay the per-incident cost, but I went via Cingular support.
Once RIM have flagged your domain as a Google Apps account, any future BIS accounts set up using an email in that domain will be immediately recognized as Gmail accounts. You then enjoy the push features available to free Gmail account holders.
Add the GMail BB app to the mix and you also have a full historical archive of all your mail on your BB.
There are still a few limitations with all Gmail accounts, apps or free:
- No read/unread syncing
- Deleting from Gmail web interface does not delete from handheld. (It does sync going the other way though)
For the calendar, I use GooSync Home Page
This solution currently syncs OTA with Google Calendar and support for tasks and contacts is on the radar. You'll need the paid version to get all features including shared calendars, multiple calendars and meeting attendees.