Bit late to this thread but NONE!!!! My last commute was last Tuesday; afterwards I spent three days having lie-ins before bussing to work (in order to kill off an excess of flex-time, and to be able to carry home Amazon packages that were arriving that week and wouldn't have fitted in the cycling backpack).
Had hoped to have been fooling around on a fixie over the next two weeks, but even recycled ones were out of my price range as a Xmas pressie to myself. Might take the MTB out for a wee non-commuting spin this week though - it's been out once in the last 18 months. Neglected in favour of the sleek and light roadie, poor thing!