Just one tuner. The two-tuner version won't be available until late summer or fall (that's in general, not sure about Pittsburgh).
The charge is $9.95 for the DVR feature, but I'm not sure if that includes the box rental or if that is an additional charge (I don't even know if there was a box rental charge for the 5100???) I'll check my bill, but it will probably be a while before I get it.
I have played with the box a little more, and I've got to say that I'm more impressed than I thought I would be. I am a TIVO user, and this can't touch the TIVO's user interface, but it is a lot closer than I thought it would be.