Ian's Pizza is one-of-a-kind. There really is no substitute for Ian's. I have not tried all of the unique varieties Ian's offers, but people who have seem to really like them. This is the only place I know of that has really good vegan cheese pizza.
The price is good at a few dollars for a slice. The 12" one topping pizza I order there has varied in price. I've been charged between $8.50 (which is a great deal) to $12.50 (which isn't a great deal). On a similar note, they have the 12" pizza made quickly. It usually takes 15-20 minutes at most.
The locations are convenient, I usually eat at the Frances street location. I've also had Ian's deliver, which is quick too. But either way, there wouldn't be any other place I could order from when I wanted Ian's.
If you live in Madison you may have heard of Ian's. If you've heard of it but never tried it, you should.