The actuall tour was great. As I wasn't in Houston long it was nice to get a overview of the city through the sightseeing tour. The space station was great and for an adult I think it was enough time to look around. There were issues with both buses which meant we were kept waiting for a long time.
The tour bus arrived late, way after both of the two different published pickup times. There was confusion over a driver for the trip out to NASA in a different, old minibus. The minibus was not roadworthy, I do not think a little picture of Jesus is a substitute for effective airbags, the airbags were held in with duct tape. See photos. On arrival at NASA they just gave us our entry tickets and raced away without any tour advice. Again they kept us waiting in the heat outside for a long time after the scheduled pick-up time. If you're only interested in NASA you should know that the adult admission is 36 and I'd guess an Uber would be about 25 each way, safer, more comfortable, better service and allowing more time at the attraction.
This was a really good city tour and the time at the Space Center was enough. The only reason I haven't given 5 stars is because the pick up location is a bit confusing and when we called them when we arrived at the hotel they were quite rude and unhelpful. It would be helpful if they added information on the pick up location like a bus will collect you at 10am and no guide will meet you before, they will be on the bus. Also I think they should give you some info about the space center like tips on where to go first etc. as they just give you the tickets and your timed ticket for the tram but that's it and we didn't realise that you can go on the tram at any time.