It seems that all HL mods, files, and updates, along with any other product ValVe releases, will be downloaded through Steam.
There are a few points that I do like about 1.6 on steam though. Getting into a game of CS seems faster, and I like the server menu. Getting out of the game is also 10x quicker than 1.5 (All I have to do is press esc then click Quit Game without having to go back to the main menu to exit. Nice.
There are some good and bad points the the riot shield. I think its cool how you can stay behind the shield, line up a headshot, then pop one into the guy's skull. Its got its good and bad points. Its nice and tactical. So I say keep it.
I say away with the new guns. The famas and the other T gun are freakin weak.