UPDATE - Looks like it's back. Skyrim and Deus Ex are now both available for under $10. Merry Christmas!
Hope you weren't planning on buying - or in some cases playing - any new PC games today, because Steam's servers have either been down or crushed for much of the day. The service's support Twitter is silent - maybe it's got the day off - but you don't have to look far to see reports of people struggling to get online.