I'm just doing the upgrade at the moment: the download was 3.4GB and was maxing my connection, but the install has taken an hour so far, but this isn't on an SSD. The process looks like it's coming to an end soon.

that's going to vary highly depending on hardware and your link speed, but I just did in on 3 relatively newer PC's with SSD's over a 30Mbps connection, and it took between 30-45mins.

I did a fresh install from MSDN iso onto a disk cleaned with diskpart from a USB stick (see [1]). I didn't do an upgrade. I wouldn't ever upgrade Windows manually after a screw up going from Vista to 7.

To do a full clean install on my Lenovo T400 with Samsung 840 Pro SSD off a fairly old Sandisk Cruzer took less than 10 minutes.

[1] http://wudt.codeplex.com/