Root, then install every custom rom you can find. Use each one for a day or two, then decide which one suites your needs best.
To be thorough, make sure you check out the other forums as well, like mydroidworld.com, and xda-developers.com.
Some roms are duplicated between the sites, but some are unique to each site.
Most of all, read the posts from others, but don't get sucked into "which rom is best" and "this rom is better than that" fights. It's all opinion, and every rom I've tried is great. They all have some tweaks here, or compatablilty there that set them apart, but give them all a fair chance and see what you like.
Apps I recommend:
Droid Overclock by jrummy
Droid X Bootstrap
use it as you would the OG droid. if you had unrooted droid, dont root this one. if you rooted it, read up, as the rooting/romming for this is slightly more complicated than the droid 1.
i would personally get rid of the launcher right away as the stock launcher makes the phone feel laggy IMO. get ADW or Launcher Pro or grab the gingerbread launcher from the market for that stock feeling.
I just did the same thing, and LOVE IT. Should have done it last fall when my contract was up. I got mine used on Ebay, so I still can upgrade anytime I want to a new phone. Now with the X, I'm gonna wait even longer, till probably the Tegra comes out. Could be a LONG wait....lol
I wouldn't bother changing the ROM myself. I must have flashed the ROM 50 times in my TouchPro 2, but I see no reason whatever to do it in the X.
I use LauncherProPlus with the stock ROM & some tweaks & my phone is every bit as fast (& none of the bugs you get with any custom ROM) as my bosses X with a custom ROM (I know, I installed the ROM for him)