Linux has to start somewhere with a big commercial supporter. I would even re-purchase Valve titles if they did this to show my support of the move.
I will however NOT purchase titles that are simply wrapped in WINE or something similar, much like EA does with their titles on OS X. It shows little work or care for the platform when they do things like that.
Btw, with a few exceptions these aren't different 'versions' as in they can mostly be installed right along next to other 'versions' if you want. Oh, and one doesn't loose features by installing one vs the other.
Backed up the system lately?