My DS is 3.4 and is reliably dry during the day now [this has only been for about last 2 months though].
But the poos, oh the poos!
Just now was a perfect example. He obviously needed a poo about 2 hours ago but denies it, always has something better to do.
Sometimes I can encourage him onto the potty but once he sits down it is like he completely loses the urge to poo, it's quite bizarre.
He usually asks me for a nappy [a pull up actually] and I do oblige him because otherwise there is likely to be a poo explosion on the floor [from prior experience]. However I tell him that if he wants to he can pull the "pants" down and do a poo on the potty or toilet like he does a wee... He listens to me and you can see him considering this... but...
...for next 2 hours he will get the urge to poo which prompts him to run around in a circle for a while until the urge passes 
This continues until I suddenly hear a sound of stamping feet as the urge to poo becomes too strong to ignore and his anal sphincter cannot hold the poo back anymore. He then makes a quick dash to the back of the sofa, crouches down and loud grunts akin to a woman giving birth to a ten pounder ensue.
Then quiet and a sheepish little boy pokes his head around the sofa to see if anyone was listening/watching [How could we not, it is so dramatic!].
He will then ask me to clean him up.
DS starts nursery in September and I actually think it will take peer pressure to convince him to start pooing on either the potty or toilet.