One of the biggest problems with the Dobs is they have really bad field rotation, that is the field rotates as the scope tracks the stars. Mel Bartels controller can be used to correct this but its quite fiddly, and unless you are mechanically minded it does get quite difficult to setup and install. The ServoCAT system is a great little add on for trus style dobs, could work with others I guess. Mainly designed for the Obsession style scopes this little unit attaches to the Alt/Az surfaces and drives it effortlessly, unfortunately you need the Argonavis DSC to do GOTO's and make it track, which is a real shame. But for simple movements across the sky its ideal, but it does not have field rotation motors. There are quite a few different systems to use, dob driver is an excellent alternative to mel bartels system.
Anyway check them all out.
http://www.bbastrodesigns.com - Mel Bartels Scope and Scope II
http://www.stellarcat.com/ - Home of ServoCAT.
http://homepages.accnorwalk.com/tddi/tech2000/ - Links to Dob Driver II and other stuff.
good luck.