Stayed in Nizwa overnight on our way from Sur to Muscat. It's located about 15 minutes by car outside of Nizwa. Our apartment - bedroom, bathroom, kitchen, living room, was huge. Fridge, microwave, electric kettle, some cups and plates - no coffee or tea. Every room had A/C. Large Tv with some English news channels.
The bathroom had modern fixtures but was very impractical - impossible to take a shower without getting water everywhere. He king size bed had nice sheets (duvet) but a fairly hard mattress and pillows. If you get there after dark, it's a bit tricky to find the right spot to turn off the highway. There is a huge dirt lot in front of the hotel with a very narrow dirt entry road with a ditch on either side. The building is well lit but not the entry road. If you're not careful, you'll end up in the ditch.
Still, it's a good place to stay if you're planning a trip up Green mountain. Only about a 10 minute drive to Birkat al Mawz.
There is a restaurant next door.