Cyanogen is the godfather of all other ROMs... It is AOSP (Android Open Source Project), so it is based off of the pure Android source code. No overlays that are added by the manufactors (like Blur, or Sense). It has a lot of features that most other ROMs do not have.
Some of the features have made there way into other ROMs (the biggest one off the top of my head would be the Power Control Widgets in the pull down bar). CM is simply a great made from source ROM and gives most others a run for it's money.
I used it almost exclusively on my OG Droid, as I could never find a ROM that had the features I loved from CM. With that said I'm actually liking Sense right now (and loving Das BAMF) so I'm going to probably wait a while to flash CM 7 on my Bolt.
Right now the build is extreamly Alpha, it will work but you might have some issues. If you haven't ever used CM I would wait until it is in a stable release, judging a ROM based on an early alpha isn't fair.
Edit: Also note that this will remove every single bit of Sense from your phone, you will not be able to use any of the HTC widgets or skins. This ROM is pure vannilia Android, as Google intended it (with lots of cool features and fixes).