I received my first G lens today, the 70-300 f/4.5-5.6 G SSM. I've been drooling over G glass ever since I had my Minolta QTSi and going ga-ga over the 85mm f/1.4 G.
The box scared me. It is really really big! The lens itself takes up half the length, and the other half holds the hood and pouch.
The only lens I have that I can compare it to is my beercan. As you can see, the G is chunkier but at 70mm it's a bit shorter. It also weighs more than the beercan so if you thought the beercan was heavy, look out!
Zoom the G out to 300mm and it grows to be a couple inches longer than the beercan. The beercan of course zooms internally.
Here's the kicker. Put on the included lens hood and it becomes monstrous.
It comes with a felt lined leather pouch.
The G is absolutely solid and the build quality is superb. It's like a luxury car of lenses. The zoom is tight enough that I don't think it'll creep much when carrying. Once you grab the large zoom ring (which is towards the front of the lens, and the focus ring is to the rear) and actually zoom it it is very smooth, though it takes a bit more force than other lenses.
The SSM focusing is incredibly quiet. I had to literally put my ear within a few inches to hear it. It's pretty fast too. I'd say a good bit faster than even the beercan despite it's smaller apertures (I can't say for sure though until I can get out and compare them in real life situations). SSM has something to do with it I'm sure, but the focus range limiter seems to really bring it to that next level by preventing focus hunting throughout the whole range.
AF full range, AF 3m to infinity, and MF are the three settings on the switch. No need to switch the camera's AF/MF switch. Also, the lens allows full time direct MF. That means you can manually focus at any time regardless of which mode it is in. If you are in one of the AF modes, it will AF again the next time you depress the shutter half way. The focus ring also does not move at all during AF. Additionally, there is a focus hold button on the side of the lens. a700 users (and a900 users I'm sure, but don't know about the others) can also go into the menu and change the focus hold button to be a DOF preview instead.
The lens is a good match for the a700 w/grip IMO. It's a little front heavy, but it feels comfortable when held in shooting position. Again, with the hood it looks nearly twice as large as without it.
I hope to find time this weekend to go out and put it through some real world uses.
EDIT: I forgot to mention that this lens makes a perfect companion to the 16-80cz. They share the same 62mm filter diameter.