I've used Android Assistant, which has a number of features, including a task killer, but I don't use that function any more. It's pretty much been established that they don't really help, and may hurt battery life. Once an app is initialized and in memory, it doesn't use any power in the background and just sits there ready to be called upon (unless meant to do background work like sync'ing email, Facebook, weather, etc). So killing them often times mean they will re-initialize on their own, which takes up more power than letting them sit. The OS is designed to use as much ram as it can for this reason and why task killers are not recommended.
A cool new feature in ICS is you can disable bloatware apps completely. They aren't uninstalled, just prevented from opening. Perhaps this will suit your needs. Go to the Manage Apps option from the settings menu. Go to the All tab so you see everything. Then for each app you want disabled, go into it and first uninstall the updates if applicable, then you will get the option to disable. Hope that helps.
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