I got mine for free from verizon because I called them really pissed about how short my batt life was because I'm always playing around on my phone. They sent me the extended life batt and I would have paid a lot to have it. My phone lasts 2-5x longer than it did before and I would be screwed without it with all I do on my Droid Inc.
Take the plunge.
Edit: And I am definitely getting that 3500mah batt. for 26 bucks you can't go wrong, I didn't even know that was around.