This was my second time in Old Town Hostel, and I could not recommend it more to anyone traveling to Tbilisi. It's in a perfect location, the facilities are better than my bathroom at home, and the atmosphere is warm and down-to-earth. Most importantly, the staff consistently went out of their way to make my stay in all of Georgia memorable. Both times I've been, I've made some very close friends in this hostel thanks to the friendly environment.
I had the best time at Star Hostel - the staff is more than accommodating and very helpful, there is free breakfast and free Rakija, which someone will always be willing to drink with you. It's the perfect spot to explore the city from, and easy to get back to after a big day. Fantastic place.
I had the best time at Old Town Hostel. The staff was extremely accommodating and friendly - I eventually went with them on a trip to Batumi after we all made friends. It's a great place to hang out, filled with interesting and friendly people, and the location in the middle of old town was a perfect base from which to explore Tbilisi. This was definitely one of my better hostel experiences.