I moved my company to Austin from NYC a year ago. Not one event have I been to where Gowalla was mentioned.
In terms of other startups, we have Other Inbox, Infochimps, WPEngine, and a number of other things that are relatively quiet. In terms of "big" players, we have Facebook, Evernote, Zynga, some of Sony's game dev (DC Universe Online started here), and Ebay/Paypal is moving in. OpsCode and Mozilla both have lead evangelists here too.
And there are probably dozens of things I'm missing..
Disclosure: I'm a Developer Evangelist for Twilio and based in Austin.