You guys should re-read the article on Advanced Task Killer.
It does help with battery performance only when it's set to kill certain apps that consistenly pop up, even when you don't allow them to or sync automatically, a lot of times, they'll open up by themselves by force.
Some apps that do this are Craigslist app, Amazon mp3, HTC Stock app, Sprint Nascar app, etc...
Now, if you're rooted you can delete those apps off your internal stock memory (Crapware apps as they're called) with Titanium Backup free app (Back up ALL your stock apps tho, just in case you need to send in your phone for a new one. Sprint might deny you a new one if they see S-off. So unroot and install all stock apps before sending your phone back).
You can also FREEZE apps too on Titanium Backup Pro ($3-5 app I think) so they don't open at all without you doing so manually.
If you don't wanna pay or can't find Titanium Backup Pro, Android Task Killer for froyo is a cheap way to turn off pesky apps that turn on by themselves and they will help with battery life, in a minor way, but they will. Just check which ones do this and 'IGNORE' the apps that you don't want ATK to touch or turn off.
You just have to watch out for which ones are opening up and constantly syncing without your permission by going to your 'Apps Running' list (You can use ATK to see also)...They eat up battery and you won't even know it.
If you set your ATK to AGGRESSIVELY KILL ALL APPS RUNNING, thats when you're doing it WRONG.
By doing that you're just making all the apps start over again and again and again...., and in turn, killing your battery because you're constantly turning on the same apps on and off.
There's more lil tips and tricks, but they become common sense after a few hours of noticing things here and there.
Long read...Sorry.