Bluetooth on or off really depends on how your using it. I only shut BT off when I'm on a plane and it doesn't have a significant impact on my battery life. However, I'm only using it for a headset, not listening to music or lots of Internet sharing/syncing. The combination of the headset you have and how you're using it will definitely have an impact, but the drain can be manageable (I use a Plantronics Discovery 655).

I also think manual syncing would be for those that really want maximum battery life and don't mind having to force a check for e-mail. I've got mine set at 15 minutes and I can go at least one day without a charge (depending on calls).

For me, the killer is when I'm using the GPS. That usually means the screen is forced on and that really kills battery life. If you've got anything that's forcing the screen on (keep the phone where you can see it to determine if that's happening), that can really cut into battery life quickly.