How good is Bioshock?

Good enough to be BANNED from Valve's offices (Bioshock was made by 2K Boston/2K Australia). Apparently it was so popular, it was interfering with productivity. Valve promised to give every employee a copy once their work on Orange Box was finished. Talk about a rousing endorsement from a competitor!

Full story here:
http://www.xbox360fanboy.com/2007/08/28/work-at-valve-no-bioshock-for-you/