Task-killers haven't been advisable on Android since Gingerbread, around 18 months ago, so that is taken care of for you. Battery life on the Galaxy Nexus (yes, even with LTE), the Galaxy S III, One X, One S, and a few others is much better than the last round of high-end BlackBerries. Especially when considering the Bold 9900 battery life.
I'm looking forward to the +CrackBerry.com
review on the One X. The perspective will be nice from someone who is more accustomed to the phones I replaced with Android devices.