I've built a couple of the control boards using the RepRap Gen7 board
http://reprap.org/wiki/Generation_7_Electronics and was pretty impressed by the quality of instructions. There were a few hiccups uploading the bootloader and firmware, but the board works as promised.
To be perfectly honest, you can purchase COTS control boards for only a few dollars more than making your own, but where's the fun in that???
I'm using the boards on an "own design" printer... it got put on the back burner in September, but I had the X and Y working nicely. Maybe I'll finish it this summer and post more here later.
Jason
P.S. My first printer was a Solidoodle 2, which (once I fixed the lousy workmanship from the factory) provided good service if not great quality prints. We have recently acquired two Afinia H480 printers and I have found their print quality... particularly their ability to separate raft and support material when using the Affinia branded premium ABS and PLA to be amazing. (Mind you, they cost twice as much and are two years newer than the poor old Solidoodle, so I do have higher expectations for them!)