I try to use it all the time when typing, the only problem is I also use a Radtech ScreenCleanz cloth to stop the keys marking the screen when the MBA is closed, but I can't close the MBA fully using both, so I have to remove the Moshi Clearguard first, which is slightly annoying.
Also, I've only had my Moshi Cleaguard a week or so, but its already starting to look cloudy/dirty and from what I've read is not so easy to get it looking clear again, which is a shame. I'll still carry on using it, though, better than having shiny/worn keys...