Ganesh Himal Hotel
I was in this hotel for two weeks in September 2010.
It's situated close to Thamel, away from the hustle and bustle and about 10 minutes from Durbar Square.
It's clean and has a very friendly environment. It has a pretty garden that's ideal to relax. The restaurant is also highly recommendable, as much for it's Nepalese food as for its continental.
Also, there's a good price-quality ratio here.
Without a doubt, I would return to this hotel if I visit Kathmandu again. Very recommendable.