I'm in some danger of waffling on forever about the G1's many features, but this is a review not a sales brochure, so let's get down to the nitty-gritty and talk about the things that really matter; performance and image quality.
The G1 starts up in just over three quarters of a second, which is impressively fast by compact camera standards, although it is a little slower than most DSLRs. It wakes from power-save mode just as quickly, and shuts down in a little under two seconds, which is also pretty swift.
As I've already mentioned, the autofocus system is amazingly fast, which helps the G1 to have a very impressive shot-to-shot time. In single-shot mode, shooting in the highest quality Raw + JPEG mode it can maintain one shot per second, while in JPEG-only mode it is slightly faster at 0.9 seconds per shot. In continuous mode it can maintain three frames per second in both Raw and JPEG modes, although using Raw mode does limit it to a seven-shot burst before it has to pause to empty its buffer.
Thanks to a very bright AF assist lamp the G1 will focus in total darkness at a range of about four metres, but even at longer ranges its low-light focusing ability is very impressive. I was hard put to find any situation in which it failed to focus quickly and accurately. It's a very impressive performance from a contrast detection system.
In terms of picture quality the G1 is every bit as good as I'd hoped. It has a 12.1-megapixel Four-Thirds Live MOS 4:3 aspect ratio sensor measuring 17.3 x 13mm, with a built-in supersonic wave cleaning mechanism, similar in size and ability to the sensors found in the Panasonic L10 and Olympus E-System DSLRs, so as you might expect the image quality is comparable with the E-520. Lens quality too is excellent, and both the kit lenses (14-45mm and 45-200mm) produce superb edge-to-edge sharpness with no noticeable chromatic aberration, which is more than can be said from some other manufacturers' kit lenses.
Typically of Four-Thirds sensors, dynamic range could be a bit better, but shooting in Raw mode allows a lot of shadow detail to be recovered from high-contrast shots without introducing too much image noise. In fact the G1's noise handling is the most pleasant surprise. Some Four-Thirds cameras have had a bit of a problem with high-ISO noise compared to similar APS-C sized DSLRs, but the G1 produces excellent image quality right up to 1600 ISO, and even at the 3200 ISO maximum setting the images are quite usable. While the overall image quality isn't quite a match for the very best full-sized DSLRs it is certainly more than adequate for any semi-pro or serious amateur, and much better than even the best high-spec compacts.
To conclude, I'm immensely impressed with the Panasonic G1. It's a very accomplished little camera that succeeds brilliantly at its objective of providing a real alternative to a full-size DLSR. I have been using it over the past few weeks, taking it on some long walks across Dartmoor, and I've found its low weight, fast performance, excellent handling and superb image quality ideally suited to my kind of photography. The only thing that would put me off buying one is the price. At nearly £500 for the basic single-lens kit it's about £200 more than an entry-level full-size DSLR, which is a lot. The question is if it's more than people are willing to pay for the camera's obvious advantages.
The Panasonic Lumix DMC-G1 is a revolutionary camera that delivers on its promise of SLR-like quality in a compact body. Build quality and design are up to Panasonic's usual exemplary standard, and despite its small size the camera handles well. In terms of performance and especially image quality it matches other Four-Thirds system DLSRs. The only downside is the high price compared to an entry-level full-size DLSR.