I was nervous at first, too. Do A LOT of reading until you are comfortable with it, then go for it. Better battery life, almost no lag, more phone features. I love my phone now. I have rooted 4 of my friends' heros. They love it. Once you do one, you think, "what was so hard about that?" At least that's how I was. I am running CM6. Tried fresh and Zen, they were okay, look similar to factory, just don't lag like factory, and better battery. I always went back to CM6. If you flash CM6, I recommend getting Dialer One. The rom doesn't have a smart dialer.
Root, make a nandroid, and start flashing. You won't regret it.