I went to Sri Lanka for 6 weeks over the millennium in January and had a fantastic trip with friends. I don't know if things have changed much since then - but public transport seemed a bit scarce? The only way to go touring from the coast (Unawatuna) to see the tea plantations, Kandy and all the ancient sites inland was to hire a driver and haggle for a package price and do it all in one hit at a bit of a pace.
I have some friends who would rather go off at a slower pace by local bus/train and then you can linger a while longer in each destination?
I recall taking the train from Colombo almost all the way to Galle via Mount Lavinia and then a rickshaw onwards to Unawatuna and a rickshaw on to Marissa, but I did not see buses anywhere?
Since the devastation caused by the tsunami I know things will have been re-built and may have changed somewhat. Any advice from recent visits will be much appreciated.