Beta came out an hour or so ago for those with keys.
First impressions: It's all right actually. Feels very CoD like in terms of the menus and stupid crap all over the screen such as achievements etc but thats been in Source for a while I hear. Recoil is anybodies guess. I always felt 1.6 had the recoil bang on what a game should be like, CS:GO feels very random in that respect, almost as if they have gone for a much more real life feel. Hit boxes are also a little odd but I'm sure it just needs getting used to. You also haven't got a hope in hell of hitting much whilst jumping.
New buy menu is actually surprisingly easy to use with a mouse but I will still use the normal keyboard way (although they have moved everything around). The beta only alllows you to join a random server or create your own LAN game which it fills with bots. You can create a casual or competitive game (changes start money, buy time, roundtime and MR) and I'm sure with Hamachi it will work online. It doesn't show ping yet (apparently there will be a representation of what your ping is soon, I expect it to be the shitty CoD signal system).
The guns seem a little underpowered which was a complaint from the initial testing, it's been done that way to make you try other guns rather than AK or Colt. The Molotov is great and certainly stops people from rushing. The decoy grenade (it makes noise of a gun every few seconds and then finally explodes but no damage) should be good in PCW's and matches.
In terms of graphics and performance it is absolutely fine. Looks a lot better than Source but it isn't going to beat Crysis but then CS is about gameplay rather than graphics. With V-Sync off I was hitting 200 - 300 FPS (Core i5 3.3GHz 2500K Sandy Bridge, GeForce GTX570, 8GB RAM) with no drop in smoke or during gun fights.
Sorry about the blurryness, the real game is a lot sharper but I've had to change the res down to fit properly: