Overall, I really do like the G1. The size is ideal and it handles very well. The EVF is large (similar in size to my 35mm film bodies) and works very well for both composing and focusing. It's actually the best VF I've ever used for precise manual focus even without using the MF assist function (which zooms in to give better focus indication). Image quality is almost as good as my D300 was (really identical to ISO 640, then falling off as the ISO gets higher). The click-wheel UI really makes a huge difference in how usable a single-wheel camera is, allowing me to switch between Aperture and Exposure compensation seamlessly. It's a bit too easy to click though, which is its only downside. Gotta say I love the MF assist function, and the fact you can actually compose in true B&W by picking a B&W Film Mode which sets the EVF/LCD to B&W display. That's a killer app for B&W shooting, no more guessing as to what things are going to look like.
Overall I rather like the camera and it will be my light carry/travel camera for the foreseeable future.
Too easy to change settings. The mode dial needs a lock, or at least stiffer detents. I find it switching to P or S modes too easily. Ditto the drive mode switch, which can easily be bumped to the next setting. I've already mentioned the click-wheel's sensitivity. And also the eye-detect system for auto-switching from the EVF to the LCD is too sensitive, I've had to disable it as it won't let me use the LCD in gut-pod mode (braced against my stomach with the LCD as a waistlevel, a favourite way to shoot in low-light).
Insufficiently configurable. Panasonic should give some more configuration options, particularly for the Film Mode and Fn buttons. Film Mode is only really useful to JPEG shooters as it allows switching between JPEG rendering settings (which also affect what the EVF/LCD do), but this is accessible from the Quick Menu button next to the Film Mode button anyways. Love to see it become configurable. Ditto the Fn button, which has too few options. MF Assist activation should become one of those options at least, giving 1-button access to it (currently you have to hit the AF button then the Fn button IIRC to activate MF assist with lenses which can't activate it automatically).
I've got 3 lenses for it at the moment, two are 4/3rds lenses using the DMW-MA1 adaptor.
The kit G Vario 14-45mm f3.5-5.6 OIS Aspherical
The Zuiko Digital 25mm f2.8
The Zuiko Digital 40-150mm f4-5.6 ED
I'm very impressed with the kit lens, it's surprisingly good for a kit lens, is tiny and well built as well (metal mount and part-metal barrel). The IS is effective down to fairly ridiculous shutter speeds (1/2 second is quite repeatable) and the colour, contrast and resolution are at the level of a mid/high end consumer zoom rather than a cheap kit lens. I don't much like focus-by-wire though, no DoF markings and so-so feel. Also comes with a nice petal hood (but no polarizer slot, unlike the great Pentax hoods) and a pouch, which is a rare bonus at this level.
The ZD 25 is a lens that I try to love and fail. It's small (25mm long), even with the MA1 converter it's smaller than most 50/1.4's. Handling is overall decent on the converter, Oly sacrificed a lot to get the largish focus ring. But the 43mm filter size is brain-dead, I can't even find a bloody step-up ring to a useful size for it. And the lens just doesn't deliver optically. The 14-45 outperforms it optically. It's only redeeming qualities are size, speed (the pedestrian f2.8 is still noticeably faster than either of my other lenses) and the good close-focus performance, it focuses to 0.2m, vs 0.3m for the 14-45 and 0.9m for the 40-150. Frankly this is the worst normal prime you can buy today. And it's not even that cheap at $279CDN.
The ZD 40-150 was a pleasant surprise. I'm not much of a long-lens shooter so I got this for $129 rather than getting the G Vario 45-200 OIS that is the other currently-available m43 lens (and is $399) or one of the better Oly lenses (the 70-300 or 50-200). It's smallish (comparable to the Pentax 50-200 in size) with good handling compared to similar lenses (real focus ring, decent all-plastic build) although it does have a plastic mount. Comes with a nice deep and reversible lens hood (Nikon, Canon, learn from this. Pentax, Panasonic and Oly understand than even cheap lenses should come with hoods). The shocker with this lens is optical quality. It's sharp, has good colour and contrast. A surprise in an ultra-cheap kit lens (this lens is the 2nd lens in the Oly 2-lens kits). In fact it puts the ZD 25, which costs more than twice as much, to shame optically. If you need a small or occasional long lens for a 4/3rds or m43 kit, get this little gem. You won't be disappointed and you won't be out much either.