There are some notable startups, but no real Startup Culture to speak of.
There are some ++s:
- Cost of living is relatively low
- Modern luxuries, infrastructure, mobility, etc. afforded by a large metropolitan area.
- Central location, with major airports (AA and Southwest are based in the DFW area)
- Strong technical economy (TI, Lockheed Martin, telecom)
- UT Dallas, UT Arlington, SMU
- Mark Cuban?
In my personal experience, I work for a startup in Dallas and we are doing quite well (profitable, growing). We're also hiring for full-time, permanent developers.