If you're new to Olympus, most day-to-day features are selected from the info panel using a combination of the various buttons and the command dial. Olympus was one of the first to offer the option, and it remains one of the best systems; being both quick and intuitive to use.
Picture quality isn't necessarily an improvement over the E-520, but there are differences. For one there's more detail at lower ISOs but the incidence of noise is increased slightly at higher ISOs. That said, Olympus has both altered and improved noise reduction algorithms, as the once distracting coloured speckles are all but eliminated (with the exception of the deepest shadows) from out-of-camera JPEGs up to ISO1600.
Raw files have a little more detail to give, and have more dynamic range than I expected, though this can be seen to a point with the results of the shadow adjustment technology at work using the Auto Gradation option. Dynamic range doesn't equal that say of the APS-C D90, but the image integrity (colour rendition, tonality and the rest) is very good, even at high ISOs.
Metering tends to favour shadows, often clipping bright highlights but at least it's a pretty consistent result, and one you can compensate for if need be. The bundled Olympus Master 2 Raw conversion software is often overlooked as a reasonable, if a little clunky utility. If that's not up to scratch you can always plump for the latest edition of Photoshop's ACR plug-in for Elements, or if you can stretch for the full version then, Photoshop CS4.
Although according to Olympus the E-520 is staying in the range, in many ways the E-620 can be seen as the natural replacement. Inevitably some features have filtered down from the E-30, which is a good thing but that camera is significantly larger and heavier and a good deal more expensive.
So while the E-620 fits well into the Olympus line-up, it has to go head-to-head with the likes of the slightly more expensive yet video-enabled 12MP Nikon D5000 and 15MP Canon EOS 500D. Both are extremely strong contenders for your cash, but unlike previous years the differences now maybe just too close to make the call, unless video is your thing.