It's hot and humid, but where in Texas isn't? You'll adapt to it. It's a great city, so don't buy into the "it's dirty" stuff. There are dirty areas and very nice areas. There are bad areas and very good areas.
The real estate prices are incredible - some of the lowest in the country. I have a 3k sq ft house that was purchased for just under 200k in a great part of town. Gas prices are lower, traffic is better, etc.
There is good and bad to every city, but base it more on people who have lived here rather than people who have visited the riverwalk a few times.