Spent quite a bit of time in Kigali a few years back, stayed in the Novotel and Des Mille Collines, they were not bad at all. Was there at the beginning of 2007 on a charter and stayed at the Serena hotel, which is very close to the Des Mille Collines (walking distance). This is definately the best hotel in Rwanda by far in my opinion and is comparable with 1st world standards so try stay there. A visit to the genocide museum is very interesting, you can find out about the history of the country right back to the colonial times.
As for dining there is an indian restaurant ( can't remember the name but the hotel staff and taxi drivers will know) which has a very nice atmosphere and superb food. Take cash dollars as mentioned in previous posts and look forward to your trip, Kigali is definately one of the better places in africa to visit