We stayed at the Volga Hotel in August 2006. I had reserved a room simply by sending an e-mail. This hotel is very good value for the money. First of all, it is really easy to find it, conveniently located within walking distance from the railway station. There is also a big supermarket nearby, and the city center (and beautiful Kremlin) is only 10 min away. The hotel has been renovated recently and it was very clean and confortable (and with hot water, which was not the case in the previous hotel we stayed in). A russian buffet-style breakfast was included and was very good. Surprisingly, there was no check-in or check-out time, they gave us the room for 24 hours : we arrived around 20:30 and could stay the following day until 21:00, which was very convenient because there was no need to put our luggage in a locker at the train station. Another important detail : they will register your visa in a few minutes.
If you want to visit Kazan (which I highly recommand), I recommand this... more