If you plan on visiting St. Catherine's monastery and climb Mt. Sinai, then by all means include an overnight at the monastery hostel. It is wonderful!
We arrived Saturday morning around 10am by jeep with our hired guide and bedouin driver, and quickly toured the monastery before it closed at noon. The Burning Bush was amazing to see. I didn't know it still existed. Hard to fathom that we were here, a place so remote and historic. We even saw the well where Moses met his wife, as it too is enclosed within the high walls of the monastery.
The monastery grounds are very peaceful. Huge mountains loom in the background. Tall Cypress trees distinguish the surrounding area as a holy site, as they supposedly only grow in areas believed to be holy. The hostel is a short walk from the monastery. There is a dining area with long wooden tables and benches, and several dormitory and private rooms.
We were the only people staying overnight in the monastery. Our room had two twin beds and a private bathroom with a shower. There was a window without a screen. Cost was minimal, around $25 US for lodging and meals. It was very clean, simple and perfect.
We were gone all afternoon, hiking up Mt. Sinai and exploring the mountaintop until sunset. When we descended the mountain, it was dark. In the dining hall, we were served a late dinner of spaghetti, meat links, bread and water. It was strange being the only ones eating in such a large hall.
Mosquitoes kept us awake rather late that night, but we fell asleep around 2 am (just when most hikers leave to climb Mt. Sinai to avoid the heat). At 7:20 am the next morning, we awoke to a slight earthquake which sounded like a big truck with a noisy engine.
Breakfast was served in the large dining hall. The meal consisted of a hard boiled egg, pita bread, humus and olives. We wandered around the monastery grounds until our guide led us to an area near the entrance of St. Catherine's where we saw a section of mountain that was carved into the likeness of a calf. Our guide told us the story of Moses, and how he brought the Israelites here to camp out at the base of the mountain while he climbed Mt. Sinai where he received the Ten Commandments. While Moses was gone, his brother Aaron made a sacrifice in the form of a golden calf for the people to worship. It was interesting to hear the Exodus story told from a Muslim perspective.
Other hotels are quite a distance from the monastery, the closest being 3.5 km away in Al-Milga, with reportedly infrequent taxi service. I think you will miss out on the overall feel for the place if you don't stay here. I found the hostel to be very peaceful, remote and wonderful.