Location is not the best if you want to visit Colombo's city center, it's a bit more in the business area. But, enough shops around and close to a beach. Hostel has a great kitchen/common area where they serve excellent breakfast. Dorms are small, no atmosphere in the halls & that area of the building. Fine for a night.
We stayed 4 nights at Clock Inn Colombo as a couple. Was a very comfortable stay, nice clean room, hot water and A/C, friendly and helpful staff, free tea/coffee. More a budget hotel than a hostel as others have mentioned. Located in Kollupitiya (Colombo 03) - plenty of restaurants/shops nearby but about a 45min walk or 300-400LKR tuk tuk to fort or galle face green. If eating nearby would recommend hotel pilawoos and new banana leaf restaurant. Next time in Colombo would certainly stay again.