Why this is important and why I am not responsible for your phone exploding :(
I originally switched from an iPhone 3GS to the HTC Incredible because ATT was molesting my wallet. Only, I discovered the default OS wasn't too responsive, and there was a ton of crap on it. Aside from that, I didn't really have any complaints, and so enter custom roms and Cyanogen Mod 7 (CM7) and the point of this article.
CM7 is a customizable, nearly universal Gingerbread/Android 2.3 ROM. There's a port for almost each Android device that can be rooted. A phone being rooted is something akin to jailbreaking an iPhone. It just let's you do more stuff. I'm not talking about you pirates :(
BEFORE YOU BEGIN!
Please note than this will start your phone fresh, so you might considering backing up all of your data if you don't already have a backup. To make a backup of your apps, please consider using AppBrain.
How do I do it?
To install the rom is fairly easy. You have to (1) root the phone, and (2) install the rom. I won't explain it step by step, because there are plenty of resources. To begin, please read about more of the terminology and disclaimers here.
Rooting the phone. The software to do it is called Unrevoked Forever and can be downloaded here. After download the software, the process is described in detail at their website, unrevoked.com. It's just involves running the programs, and clicking through the prompts.
Downloading CM7. You can either download Rom Manager after the phone is rooted and download CM7 through there, which is located under Cyanogen nightly, or download it here, copy it to the phone and use Rom Manager to install it. Supposedly #29 is stable, I'm on an earlier version and everything works fine.
If you get past step one, which you should, you can backup your current phone (which is one nice thing about rooting) as a nandroid backup, which is akin to an iTunes iPhone backup, and always revert back to it if nothing works well.