I live in Houston. I stayed during the storm. Thankfully the storm more or less missed the city. Although there were obvious problems with the evacuations, by and large I would call it a success. Below I will explain why.
First, a bit about Houston geography. The city is barely above sea level. The entire city is littered with a collection of bayous and flood plains for water collection. In addition, the area south of Houston all the way to Galveston is covered wtih towns. In effect, it is more or less a giant suburb of the city that houses a ton of people. The orders for the mandatory evacuation dealt only with the low-lying areas -- basically coastal areas (Galveston) and areas south of Houston. All other areas were not told to evacuate.
Secondly, Rita came in right after Katrina. The problems associated with Katrina were still fresh in the minds of the entire Houston population, not only as a result of the national news but also because we housed about 100,000 people from the evacuation. This means the hotels and other boarding establishments were already near capacity before Rita hit. People could not simply make reservations in a town north of the city, but instead had to go much farther for alternet plans.
Mayor White -- who acted brilliantly throughout this entire affair -- called for a mandatory evacuation of the areas south of Houston. When the mayor made the evacuation call, a lot of people not in the mandatory evacuation areas also decided to leave. The estimates I have seen are around 2 million people left Houston over the last weeks. Simply put, too many people tried to leave at the same time. It's that simple. The highways, gas distribution and delilvery systems were simply overloaded.
The only organization that I know of that has actual experience and plans dealing with moving that many people is the US military, and they have a system of hardened command. When it comes to non-military people, an operation that large is a hell of a lot more difficult. The phrase herding cats applies.
Were there mistakes? Yep, there were. Could they have opened up the contra-flow lanes earlier? Yep, no doubt about it. I have no experience with traffic control policy, but I would assume that changing the direction of 2 major US Highways (45 and I-10) is not a simple affair. Not only would this decision effect Houston-Dallas and Houston-San Antonio traffic (three of the largest US cities), but the I-10 decision also effects commerce along the entire south of the US. That's a damn difficult decision to make and implement in the easiest of times, let alone ann impending hurricane strike. I know there are other states that have this ability, but there is a big difference here. Texas is one of the most populous states in the country with some of the largest cities all around. That makes changing the lane direction more complicated.
In addition, a lot of people who would not have normally have left did so, largely because of Katrina. For example, my entire neighborhood is not in a flood plane, yet most of the residents still left. My guess is a fair number of those from my neighborhood who left did so because of Katrina.
In short, this was an incredibly difficult situation to deal with in the best of circumstances, let alone an impending hurricane strike. I am coming to the opinion that expecting any mass evacuation to go smoothly and without a hitch is simply asking too damn much of people.
I should also add that by 4 PM yesterday -- about 8 hours prior to landfall -- all the highways were clear. This means that whatever problems arose were dealt with sufficiently so people would live through the storm.