Mercato Centrale: Absolutely, a must do. It gets very busy during regular Italian meal times, so show up a little early or a little late.

Gozzi: Still one of my favorites, as good now as it was the first time I went 6 years ago. Gets busy, especially on weekends. I ended up going on a rainy Monday a couple weeks ago and sat right down.

Sostanza: Haven't gotten there yet, but I've heard good things. It's on my to-visit list still if that means anything.

Antico Vinaio: Good bargain, 5 euro for a sandwich. It's good, but if the line is half the block, it's not that good. I think they're a little too heavy handed with their truffle creams and tend to avoid those. This is one of those places where it's great for a snack on the go, but there are other good sandwiches in the area. That said, the apartment we stayed in was a block from here, so I ate there twice last week. It's in all the guide books and anyone that has ever studied abroad probably lived off of this, so there's a hype factor that is only partially warranted.

Pensavo Peggio: Haven't been and haven't seen a menu, can't really comment.

In addition to your list, I should update my recs in the thread, but just to throw some names out there:

Del Fagioli, over by the Conad City on Via dei Tintori
La Casalinga, a block or two west of Piazza Pitti

Both have a solid place on my list any time I visit Florence.