South Austinite so I'm a bit biased, but here's my take. Cedar Park and RR are quite a ways out of the city and traffic in Austin heading north/south is atrocious and getting worse, fast. You can live up there cheaply but if you're coming for the Austin city experience, you may be disappointed. If you do end up that far north, I would recommend looking into Pflugerville, as well, which is a very nice area.

The Domain/Arboretum is between those suburbs and the city and it's a booming area these days with a lot going on. My advice would be to look near there or south of there for your housing. This gives you good commute flexibility for jobs in the burbs and the city, and makes getting into the city much more pleasant.

I think the only advantage would be cheaper housing. They are fairly typical suburbs so it all really depends on what kind of lifestyle you are looking for.

Traffic going North/South is getting really bad, so if you are wanting to be central/downtown during the weeknights you're going to want to stick around for a while and delay your commute or somehow offset your commute.

I have a coworker who lives in cedar park (our office is by UT) and fortunately for him his manager allows him to come in around 10 and leave at 4 to miss the traffic, but he has to make up for hours later in the evening.