well mine were some fake oak laminate, which had started peeling off in places, so i ripped the whole lot off, underneath was MDF, which i painted and the doors look like brandnew. I did this a good 1.5 years ago, and they still look brilliant. Painting MDF is a bit of hard work though...
If your cabinets are standard sizes you may be able to just get new doors and drawer fronts. It would be worth checking prices as you'd have more options with new doors / drawers fronts (eg high gloss, wooden, different styles like shaker, glazed, etc) than you would with just paint. It would also be a lot less mess and hassle. You might not even have to go back to your original supplier, you could just go to B&Q or Ikea.
I did the kitchen units in my last house using a small roller (1" dia) so as not to have any brush marks. Or possible take the doors off and spray them.