My personal opinion is that the apparent increase to battery life that people experience is due to the battery time remaining estimations improving after the phone has had a chance to track some charge/discharge cycles. That and not using the phone quite so much because you've finished most of your tweaking of it.
For my own experience, the battery life does seem to be improving, but the true test for me will be tomorrow when I finally get my memory card. I got a note from the post office telling me to come collect a package, I can't think of any other items I'm expecting.
For the record, I never did anything special to my battery, apart from making sure it had a full charge of at least 12 hours the first time. Although it was more like 20 hours because I was playing with it while it was charging for about the first 8 hours & I was almost draining the battery faster than it could recharge.
Anyway, if you want to know more about my opinions on batteries, read the post linked in my signature.
If you are having battery issues, try reading my post about them: