Just to get it strait, it Helix a "home replacement app" or is it different?
Yes, it replaces your current home system with a new one. The UI is largely the same, but some improvements are had. The screen auto-rotates without having to pop the keyboard out, for one. You have the ability to have up to 7 home screens too. So while everyone is crying about how 2.1 doesn't include more home screens, it doesn't matter to you who already has more home screens than the update was supposed to provide. And you get a neat little permanent app bar on the bottom. It contains 4 apps that you drag into it that is always available, no matter which screen you're on. The ability to double-tap and see what's on every screen is a nice touch too and saves time on swiping through 6 screens to get from one end to the other.
I can't get Helix Launcher to work. I had it on my Droid briefly when I was 2.0.1 and it worked, but now that I'm 2.1 I have reinstalled it and nothing. It shows that it's installed, but won't let me switch from the default home screen. Am I missing something simple?
I didn't have to reinstall it after I updated. It kept working just fine. Did you uninstall it, or something?