As the transit planner Jarrett Walker regularly reminds readers on his blog[1] and book of the same name, the real things that make a mass transit project effective are not about the particular technology being used to do the moving. The geometry of the network, its connections, and its schedule of service are what actually make it usable.
The advantages that gondolas would have in Austin is the ability to easily cross the lake and climb the hills. All without expensive rail lines (limited to 2-3% grades) and eminent-domain seizures.
Although - having drunk people flying over your house during SXSW or Formula-1 weeks might not be attractive, because of uhh, biological contamination reasons...
[1] http://www.humantransit.org