I was at IAH twice this week because we had family visiting from Orlando, and I can honestly tell you I was embarrassed for them to see our airport. They're doing a lot of construction at IAH and it doesn't seem that there's any rhyme or reason to it. Roads end abruptly and signs are few and far between.(If you are lucky enough to find a sign, there's a good chance it's outdated.)
Anthony B. (yelp.com) describes this airport as miserable - I think that's a perfectly fitting description. It's hot, the workers are rude, there are no good restaurants or shopping, and no "common area" where you can hang out with your travelers before they have to board. (Unless you count the baggage claim area. I don't because the few seats they do have are hard, plastic numbers that are welded to a bar. Makes conversation uncomfortable as you have to twist around to talk to the person on your right or left.)
Also, I've found the TSA at this location to be largely inconsistent and utterly lacking in people skills.
Finally, the entire airport has an ambiance of antiquity and dirt. Nice way to welcome travelers, eh?
Luckily, we have two airports in Houston. Although Hobby is smaller (and I think, older), I find it to have a much more comfortable feeling, the parking is easy to negotiate, it's cleaner, and it looks to be kept in better repair.
If you have a choice of airports when you're traveling, avoid IAH and fly into Hobby instead.