I'm not sure in what part of Houston you're located, but in Cypress I have used Texas RV & Car Care. I'm not sure why they have "car care" in their name, because all I saw there were RV's.
I would say good and bad things about them. First the good... Last summer I was prepping my coach to go on a long trip, and when I got it out of storage I realized the entire house power system was dead. I freaked out a bit since I was taking the family across the country the next day, but luckily the chassis system still worked so I could drive it to the Texas RV guys. They were very helpful and were able to pinpoint the problem right away. It turned out to be a blown 150A fuse in the battery compartment (which I didn't even know was there). They rush ordered the fuse from a local auto parts store, so in an hour I was on my way. They only charged for the fuse and didn't charge any labor, which I thought was nice.
Now, on the bad side, I had them remove my old tank gauge (the kind that only has 4 lights showing empty, 1/3, 2/3, full) to install a digital gauge that would give exact percentages. I was told it would take a few days and would cost around $700 of labor. After more than 3 weeks, when I picked it up, I was charged with almost $2,000 of labor. I understand it took far more work than they had anticipated as they had to basically disassemble the wet bay and tank compartments. I think they actually worked all the hours I was charged, so I don't think it was dishonest. I just would have appreciated a call telling me it was going to cost almost 3 times what I had been told. In the end, though, they did do a good job on the install.
All that being said, I would probably use them again for routine procedures, but for anything more specialized (like my gauge installation) I would be sure to get a written estimate and ask them to call if they were going to exceed that estimate.
Also, I've heard good things about RV Mobile Lube where they'll come to you and do the service, but I haven't tried them myself. I probably will next time I'm due for service.
Here are the web links:
Texas RV and Car Care Home
RV Mobile Lube - Home