I was a massive CS fan back during 1.6 and earlier. I'll give this a shot, why not.
I keep wondering why people would switch over from CS Source or 1.6. What's the incentive for veterans? It has new graphics, new achievements and a bit of COD, but that seems to be it. Is that gonna be enough for oldschool CS players?
One reason: competition.
CoD has been on a decline since CoD4:MW, 1.6 hasn't attracted any new players for years, cs:s is dying, competitively. The only 'eSports' that have been getting any real coverage lately are SC2 and the MOBA's, so for the competitively inclined FPS players it's now or never, with CS:GO. It will either put tactical shooters back up there with the other big competitive games, or it will be the final nail in the coffin if this game somehow fails as well.
What's amazing is that most communities seem to realize this and everybody seems to give this game the benefit of the doubt and really wants it to be good. The nerdrage and other stuff we're used to seeing from the more hardcore pc-crowd have all been fairly minimal, especially in the light of the more general consensus of this game being actually pretty good. Valve has been pretty amazing as well with how they are listening to the players and try to give them what they want, one update at a time.
For proper competition you'd need a big community, and right now most people are looking at CS:GO to finally bring the splintered player base back together and make FPS'es matter again.
To the average duder this all probably sounds lame as hell.... meanwhile, I'm really excited for this game's potential.