Their support is pretty bad from what I hear, but then again, so is Microsoft's. Bad support doesn't seem to be the kind of thing anyone is making decisions based on, no matter how much people like to bitch about it.
I bought an add-on to a game, it downloaded to 99% and refused to finish. I mailed support, perhaps 2 weeks later I received a generic did you try to reboot your PC response. So I listed the 10 different (including and up to complicated) things I had tried up to then and mailed back.
Another 2 weeks later I get another response along the lines of whether I've tried restarting my Steam client.
After a 3rd round I just gave up. In the end it was a network issue on their side that auto-magically resolved itself (after 1.x months)