The weather - yes, you can melt here in the summer, but unless you're a teacher when are you really outside during the summer anyway? You go from air at home, to the car, to work and back again. The "other" seasons - I really didn't think they existed here, but they do. Leaves do change colors and it does snow. Even ice storms! Spring is short but sweet.
Taxes - TX is one of the states where residents don't pay state income tax.
Space - you can definitely get a lot for your money here in terms of housing, depending on where you choose to live.
Entertainment - there are so many chain restaurants here, as well as local favorites - you'll never run out of possibilities (especially if you like Tex Mex).
Location, location, location - Dallas is centrally located so it's no more than 3-4 hours flight time to anywhere in the country. Also, it's the gateway to Central & South America.
Quick Tips:
Definitely do the touristy things at least once here - see Southfork Ranch where "Dallas" was filmed, pay respects at the Grassy Knoll where JFK was shot, enjoy a day at Six Flags over Texas (the first Six Flags), see the cowboys in Fort Worth.
Best Way To Get Around:
The only way that I know to see the whole place is to drive...read, traffic can be a nightmare at times. Since everything is big in Texas, it follows that the problems are too. All the distinct areas are so spread out - Plano, Fort Worth, West End, Deep Ellum, etc. that a car is necessary.