Yep...sand the doors down just a tiny bit so they are smooth, MUST MUST MUST use a decent primer like Kilz. If you dont the paint won't adhere, and when you need to wipe down the doors from time to time since Grease accumulates in a kitchen, you'll pull paint off.
Use smaller rollers for even coverage, and I used one of those throw away foam brushes for the crevices if you have any routed out trim or decor on the doors. Make sure you keep the doors in order of where they came off so they can go back on the same places. Surprisingly, you'll find that all the screw holes from the hardware wont match up right if you dont. Remove the hardware before you paint.
Don't forget about the cabinet frames themselves. Freshly painted doors might look funny on cabinet facing that is dingy and older. Updating the hardware can be an inexpensive update too.
For way easier cleaning/maintenance, after you have painted them, seal them with a polyeurethane (sp?) coating, and stains wont stick to the paint.
Be sure to take before/after photos so you can show them off here!