We only stayed at Thomas' Hotel for one swift night - we arrived in Christchurch at about midnight and were picking up our campervan the next day.
The staff were kind enough to arrange us an airport pickup at no additional cost with supershuttle (who are the cheapest airport shuttle in town). We got an envelope with our key in it and all the information we needed for our stay, as reception closes at 8pm (I think). Our room was clean, the bathrooms were also very clean and the hotel itself was spacious and had good facilities. The following morning, we checked out and were recommended an excellent place for breakfast (that's not in Lonely Planet). It was probably the best breakfast I have had in a long time - delicious.
Thomas' kept our bags for us for free until we picked up our campervan and drove it back to pick up our bags. Overall, we really appreciated the hospitality of the staff and it was a fabulous introduction to New Zealand.

Pros:

Good location
Very affordable
Television in the double room
Clean, quiet kitchen

Cons:

The lack of a fan or air conditioning was a problem on hot days
Limited number of bathrooms

We booked a double en-suite. This was clean and comfortable although a bit cramped with a non-functioning TV. The hostel has a large kitchen and lounge plus the usual internet and laundry facilities. Reception staff were friendly and helpful (note that they finish at 9.00 pm and you will need to make special arrangements if you intend to check-in after that time).

Excellent location - only a few minutes to the cente of town in one direction or to the botanic gardens in the other if you fancy a peaceful stroll. There is a convenience store about 5mins walk away and the hostel is opposite the 'Dux de Lux' restaurant/bar which brews it's own range of beers and has an extensive seafood and vegetarian menu.

My partner and I flew into to christchurch late at night, so a shuttle and key to our room was arranged for us, which was great.
The budget double room itself was fine, very cold though when we arrived, but in fairness it was the middle of the night. Plenty of blankets to keep us warm. We stayed for two nights though and the room was always cold, even when the radiator was on. It didnt bother us too much because we didnt spend too much time in the room.
The bathroom facilities were very clean, and so was the kitchen and lounge (both also v spacious).
The hotel was about a 5/10 min walk at most to christchurch cathedral. A perfect location!
Id definately recommend for someone looking for a budget stay close to the city.