I highly recommend a task killer regardless of whether you are using Good for Enterprise or not. However, the other posters here are absolutely right: GFE is a complete battery hog and can kill my Evo in about 4-5 hours.
I manually kill it using Advanced Task Killer after every use (and I have Advanced Task Killer scheduled to kill almost all other apps every 30 minutes). With a 1Ghz proc, it is not like I have to wait more than a 1-2 seconds for an app to start anyhow so I aggressively manage battery consumption. And, again, as I stated above, with a 3G (and even more so on a 4G connection) Good takes about 15-30 seconds to download 20 or so emails from my corporate server.
Hey, the alternative is I use a blackberry which syncs everything in realtime (not that I need that - I'm an i banker not a surgeon) but I have limited ability to do other cool stuff with my phone.