I would go for the thunderbolt if you can afford it, or wait for the bionic. I upgraded to a dx in Jan. and I am regretting it now. I use to hack the d1 like crazy, but the dx has the locked bootloader and you can't flash any custom kernals, or cyanmod, or miui, etc etc. What D1 does, DX can't... I would go back to my og droid but i have come accustomed to the larger screen on the dx and it is so much easier to type, the thunderbolt has the same size screen as the dx. Also, almost every dev I follow on twitter that had a dx has moved on to the thunderbolt, so there should be plenty of hacks and roms for it. Hope this helps.
Don't get me wrong, the Dx is a good phone, it is just a dying breed without an unlocked bootloader......