In the past, I used to overclock all of my PDAs. I still remember the days of the old Compaq iPaq and the Palm OS PDAs. Those days seem so long ago.
So, should you overclock your Android-powered Droid 2 or Droid X? I don't think that you really need to. After all, the 1 GHz processor is sufficiently fast in my opinion. Plus, overclocking will drain your battery quicker. I also believe that there may be a risk of damaging the hardware if you overclock these Motorola phones, but I'm not sure how great that risk is.
A few years ago, I used to load custom ROMs on everything. I overclocked everything. Now, I'm mainly running stock ROMs and I'm not playing around with overclocking apps. If you're dying to overclock your Droid 2 or Droid X, you can try DX/D2 Overclocker (which is a $0.99 download).