Sorry for not taking the time to read through this very, very, very long thread. So, I apologize if this was already discussed - just wanted to report in.
I got my Eris 6 weeks ago and was immediately told to install task killer.
At any rate, I still had terrible battery, despite hardly EVER having anything turned on that I would have liked. You know, like all the things that I bought it for, wifi, bluetooth, gps mobile network etc. And yes, I used atk religiously.
After maybe 30 minutes talk time, 10 minutes of mobile network, youmail and 4-5 hours into my day, I would be down to around 30%-35% power. (Battery app with %)
Anyhow, I came across a post somewhere about the App "Toggle Settings". I installed it yesterday.
Today, I left everything on
all day (since 6:00 am) other than bluetooth which was only on 45 minutes or so.
I talked at least 2 hours (probably more) and did a bit of playing/showing off with a bud that just got the Nexus.
I plugged into my car charger for about 30 minutes at 4pm.
I turned of mobile network around 6:30 pm.
My battery is at 67%
I AM THRILLED.
Sorry if the are atk lovers out there. In my case, getting rid of it totally changed my Eris.
Also - at the same time I installed "Lookout" (mylookout.com) which by the way is awesome. I do not see how this might have helped with batt mgmt but felt I should mention that.
Hope this helps someone out there!
Can't wait to see how great it does with we get the elusive 2.x!