Oooh, I have been there twice, once one my own when the war was officially raging.
I loved it, and so went back! Really really friendly; most people speak very good english which helps as my tamil and sinhalese is limited to hello/please/thanks. But even this is a lot more than most tourists... Pleeeease learn just the basics!
Anyway, I digress. AMAZING food, lovely people, Sri Lanka has loads to offer - beachy, surfy small towns, ancient history, fab wildlife, chic towns. I loved Galle, although I see Murphy did not. Colombo I'd just visit in passing. The elephant orphanage is a no-brainer, and not too far from airport. For the rest - it really depends what you fancy...
I have both hired the same driver for the whole trip, and not - ie figured out each trip as I went along. It is more the norm to hire an retain a driver, but both easy. Roads a bit scary, I'd really not want to be driving myself.
Def go! I think the tourism industry has been decimated since the war and the tsunami. People will be very glad to see you, and you'll have a fab time.