People are just way to nostalgic about 1.6 so they immediately say "well csgo isn't 1.6 so it sucks"
I put months of playtime into 1.6, I'd play it like 8 hours a day back in high school, get home from school, play til I went to bed. Sure, it's different from 1.6 but I still prefer it much better then source. Hell, I haven't touched 1.6 in a long time now and I feel I'd have a hard time getting back into 1.6 because of GO now a day.
Valve is constantly updating the game every week or two and with every update they bring it makes the game much better. They've changed recoil to make it less random, they've changed sounds, they've changed prices, guns and maps. Hell, they've taken de_nuke and took a PLAYER modified version of it and it's now available in their matchmaking. They are listening to the community as well as professional players.
The biggest downside to the game is if you get higher levels in matchmaking there are tons of hackers. So you either have to play against people you know, or join up with ESEA. Otherwise, a majority of the "higher skilled" players probably at least wallhack, if not aimbot.
Don't buy CSGO at $15 though. I swear it goes on sale every other week for at least 50% off.
The major things I'd like for them to change now is:
Pistol Fixes - I think some of them could still use some tweaks. Glock might still be a little too strong. p2000 still blows. deagle blows. 5-7 and tec9 are boss mode though.
Maps - Bring in the rest of the tournament maps into Matchmaking. Mirage, Mill, etc etc
Sounds - Could be tuned up a little better
Servers - Bringing them up to 128 tic instead of 64 tic makes registration much better. Hopefully they get around to upgrading all their servers. It's a world of difference playing on a valve server then it is playing on someones 128 tic server.