The 3day potty training program was great for us. It completely worked for Boo to pee in thd potty but it took a full commitment by me, DH, our nanny and buy in from his preschool teacher. He was a full 3 and a half. I also admit though that he still has occasional accidents but I think he often does it to prove he's in control. He got scared though the 2nd or 3rd time he pooped on the potty when he was a litgle backed up and it hurt so then he associated poop on thd potyy = painful so he began yo withold. I agree though that you need to figure out what he IS motivated by. I was shocked to discover that Boo could not care less about getting m&Ms. He cared far more about little toy bugs and when he got a little jar full of bugs he earned a tog construction crane that he coveted. We'd left the crane on a high shelf fully in view so he was motivated to poop in the potty to earn enough bugs to get ghat crane. We did have to get him on miralax per the pediatricians instructions because the withholding set up a bad pattern where he held it then would gave unexpected blowouts at really inopportune times. He's still on the miralax but I've got him now at half the d dose the ped recommended and he does fine.
Oh I also recommend the book Everyone Poops because it helps demystify the whole pooping thing. We talked a lot about how even mama pooops, even his teacher poops, even hus grandparents poop, etc.
HTH. Let me know if you need more info.
Mama to DS1 Punkin (2/04) and DS2 Boo (1/09)