I was there for about a week in January on a rented 250cc bike.
The bike was fine, but I did not enjoy the riding there very much: riding on any of the main roads is a miserable experience, there is so much truck/bus/tuk-tuk traffic in both directions that it is very difficult to pass and you end up putting along at 30km sucking down diesel fumes (and this is not in the cites, but on the main roads between towns).
It is better on the smaller roads, with little traffic and often great scenery, but the going is very slow because of the narrow, twisty roads. All the roads that I was on were generally in pretty good condition (at least compared to Russia).
Also, while I'm generally pretty good at navigation, I have to say that I really struggled in Sri Lanka. Despite having the best (two) maps that I could fine, most of the towns along the routes were not on the maps, and I got lost on a regular basis. All part of the fun I guess, but it did get old after awhile.
Overall, I have to say that I did not really enjoy the riding there very much.