Thanks for the responses.
The program says that for the rebate, they won't cover the tax you pay on whatever toilet you buy, which I thought a little odd. And they will only cover the bowl and the tank - so they won't cover the bolts, wax ring, and toilet seat ... but for a bunch of the qualifying toilets on the list, they are sold at Lowe's and HD in all-in-one packages with that stuff included. I was just wondering if anyone had been denied a rebate because of this.
Indigo - below is a link to the toilet info. No income restrictions at all. For the rebate program, they'll reimburse you up to $200 per toilet that you replace for toilets that were made before 1996. My questions above were my only concerns with this program. For the free toilet program, info is at this site as well.
City of Austin - Residential Toilet Replacement Program