I just bought a couple if used 55g acrylics for a greenhouse I'll be building next spring. For $30 each I was expecting them to be bad, but that isn't a concern for their intended use. If you saw what those tanks look like, you wouldn't be asking the question.
I know I'm gonna get it from the acrylic tanks folks (deservedly so), but the choice boils down to a list of questions you have to ask yourself, and they really aren't in any order of importance:
1. What sort of aquascaping? As Dogfish noted, there tends to be slightly less use of rocks, but certainly not absent from the FW hobby. So bear in mind that if those rocks "kiss' the viewing panes, you've got a scratch. Glass too if you're really not careful and with certain stone types.
2. Do you have/will have little ones in the house? In a nutshell, acrylic scratches from the outside just as easily.
3. Just what do you plan on putting in it? If you're new to planted tanks or tanks in general and can envision scraping algae often, even a Buddhist Monk will slip.
As for the whole repairability issue, while acrylic can be repaired, it's no fun at all. Deeper gouges will have you cursing a blue streak. Contrary to what most think, glass can be repaired as well (there's a windshield repair product that works really well), but that's no walk in the park either, and a deep gouge will probably turn into a running crack before you get to repair it.
Hopefully others on either side of the discussion can add to the list.