Abraham,
Speeding enforcement, IMHO, is much more about revenue than it is about public safety... There are exceptions, of course, but generally if you're not moving at the same speed as average traffic, that's less safe than busting the speed limit by 10 mph.
If the driver you reference was doing Mach 1, then that's different, of course.
I've had really fast vehicles - motorcycles that were capable of 60 in under 2 seconds, cars that were capable of 60 in 4 flat. And I've had really slow vehicles - including 4-door cars under 85hp as well underpowered RVs. Vehicle capabilities do influence driving style, at least in my case. Largely it changes my cruise speed as well as conditions in which I'll pass. The <85hp car, I had to plan to pass at least 1 mile in advance, literally. I don't think I've ever passed on a 2-lane road in the RV unless someone pulled off. I've largely given up speeding as I got older, mainly as I see it as "voluntary taxation" - even with high end radar detectors. If I need to save time over a long distance, I find another way to travel.
Generally, the speed of traffic on a highway is at least 10 over and in most cases, probably more like 15 over on average. I've got an RV now, and if the speed limit is 55, I drive it 55. If it's 65, I drive it at 60. From there, I generally don't exceed 65 mph, regardless of what the posted speed limit says because it's a lot of vehicle and because I pay a big fuel penalty above 65 mph. I do a *lot* of pulling off on the shoulder and I've found that Texas is generally one of those states where drivers are likely to do this as courtesy. Doing 55 in a 55, I don't feel entitled to keep my lane even if I'm at the posted speed limit. Legally, I can do it, but I don't... And I'd like to say that I'm just that courteous, but largely it's about my own safety. If I keep that lane, they'll eventually try to pass - and that pass may or may not be safe. Pulling over encourages them to pass when I think it's safe and when I'm expecting it.
One other consideration:
In Austin (and Fort Worth, Edinburgh, Beaumont, El Paso, Helotes) there is a 3-foot bicycle rule. That is, you're breaking the law if you're less than 3 feet away from a bicycle.
Bicycles have the same legal right to be on the road as cars (on most roadways) and aren't capable of meeting posted speed limits. There are places in Austin where you can be behind a bike on a 2-lane road, no passing, for 10 miles or more. Unless that bicyclist pulls over you cannot legally pass which can mean that you're stuck back there for a half hour or more. Should the bicyclist stay in the traffic lane, as he's legally allowed to do so or pull over? I had one case where they wouldn't pull over and I wouldn't make the illegal pass - so we stuck it out like this for more than 30 minutes.. Kinda an exercise in being stubborn on both sides.