I think an elevated bikeway would definitely be less terrible than an elevated train or six-lane freeway. It'd be both narrower and quieter. It would still be kind of unfortunate for those under it though, especially if they wanted to proceed with the "urban elevated parkway"-type concept (which granted is pretty cool for the people above).

That said, from the sound of the traffic problems in the article, I think Austin is going to need a lot more than just bike lanes. It's expensive, but they might need to bite the bullet and build a proper subway.