I thought I'd come back and report after a while following my switch from Nikon D300 to the Olympus E520. Please bear in mind that my comments are purely subjective. For an objective review, read Gordon Laing's excellent reports on this site.
First off, I tried also the Nikon D90 during that time - that is, I took it home for about one week, not just at the shop. So I'll start with a very quick report on the D90, although my feedback will be mainly about the E520.
D90: Impressive at first: supposedly same sensor as my old D300, same great hi-def LCD, movie...
First the movie: I got quickly tired of it and realised that I would not probably use this function that often - I have my Panasonic Lumix TZ15 for that. Second, the big "hoopla" about being able to use normal SLR lenses to film (and thus achieving bokeh and the like), is overated. What you end up is out of focus images as you zoom in or out, followed by having to manually focus. Not that good. Might be different if you use a tripod and both hands - one zooming, the other focusing - but I was using one hand, the same way as you shoot. Is one to assume that everyone will use a tripod when filming?...
A second observation is that I ended up with a disconcerting amount of blown highlights in my pictures. At the standard setting, the pictures looked washed out to me, and, as I said, the metering seemed to overexpose, even with ADR switched on.
A third observation is that the colours in Vivid mode - the way I like it when shooting scenery - looked...blown, I guess is the best way to describe them. Yes, the colours were vivid, but they had thos almost neon look to them. To me, it was not that pleasing. In short, the results didn't "pull me into the picture", if that makes sense. It left me cold.
On a more positive note - and to finish off wit the D90 - the ISO performance at 1600-3200 ISO was great, no doubt about it. That's it. I returned the D90 and got back to the Oly E520.
So what do I have to say about the Olympus E520 after a while, after switching from the Nikon D300/D90? The summary can be encapsulated into two aspects that attract me to Olympus and, in this case, the E520:
1. The colours and tonality of the pictures; and
2. The Zuiko lenses.
1. The colours. I absolutely love the colours I get straight out of the camera with the E520. They're rich and warm, vibrant and velvety. I also find the metering to be exceptional and - yes, better than what I got with the D300/D90. Especially with the new SAT mode that reigns highlights in and adjusts shadows, I have yet to get over - underexposed images. It just works. Caveat: Using SAT also boosts noise in underexposed parts of the picture - an inherent downside of underexposure, no matter the camera. But even without SAT enabled, I really appreciate the tonality and richness of the pictures I get. And to me, that's what really matters in the end: the picture.
2. The lenses. I don't particularly care if one manufacturer has a "million" lenses if none of them is the one I want. I got the Zuiko 12-60 F2.8 -f4.0 and it's a gem as a walkabout lens. Not only is it tack sharp, it also reproduces colours beautifully and is very nicely built - and weatherproof. I don't like having too many lenses, preferring to have a main lens plus a couple of more specialised ones (i.e. wide-angle, macro, etc...) and that's it. As much as I liked the range of the Nikon 18-200, I disliked its creeping and average build. If Nikon had a Gold Ring version of the 18-200mm, it might have been different. I just didn't enjoy using the 18-200 that much. The images were good, but it didn't feel tactile, it didn't invite you to shoot, or carry it as it would creep. Bear in mind, though, that these are highly-subjective comments. These are my preferences/nigglings, and I each one will feel differently, ok?
In contrast. I feel Olympus-Zuiko has a range of lenses that appeal to me in the future: in addtion to my 12-60mm, there's (in the future) the 50mmf2.0 macro, the 7-14mm and the 150mm f2.0. Besides being probably some of the best optics available from any manufacturer, they're also smaller and lighter

, comparatively, if not cheaper, alas...
Ok, so far, so good. What about the E520's downsides?...
- Noisier at high ISO. No question, if you shoot a lot of high-ISO shots (i.e. at night, etc...) the E520 might not be your best choice. I don't, so that doesn't bother me. And when I do, the 1600 ISO shots (which are not that bad, just not as good as Nikon or Canon) can be cleaned up with Neatimage or Noiseninja. Good enough for me. The E-3 is better, but as I said, if high-ISO is your thing, then look elsewhere than the E520.
- 3-point focus system. Not an issue for me, as I tend to use single-point, middle auto-focus to nail exactly the subject I want. I found that I was only using the 51-points of the D300 when shooting birds/pidgeons and passing cars, and it was more to "test" the system than by necessity (it works!

). But that's me, I prefer to shoot, in general, still objects. Plus, I don't like the choice of focus points any camera makes when framing a subject. Once again, if you shoot action, there are better choices than the E520.
- Frames-per-second (fps). Not an issue for me either. 3.5 fps is enough. See above comment about focus points, it's related, and same argument.
- Anything "painful"?...yes, the flash does not clear the 12-60mm if used too close to subject.
I will finish by pointing out a couple of features I really like about the E520:
- The way you can adjust settings via the screen. Brilliant. In addition to the ISO/WB/AF/ Metering that can be selected via the 4-way wheel, it adds up to a very fast and intuitive way to navigate the settings.
- Ergonomics. Yes, ergonomics...For my hand-size, the E520 feels much better than the D300, and, especially, the Canon 450D, which was really annoying me in this respect.
- Shutter sound. Heavy...love it...
- The way I can assign the Fn button to obtain a custom WB setting. I just press it with my thumb and shoot at a target. Quick and easy.
- The way in which the top-side wheel can be assigned to exposure compensation when in Program Mode. It's always there, and it's very intuitive to use.
- The way that you can zoom picture using the same top-side wheel. Quick.
- The way you can compare two pics side-by-side. Useful.
Overall conclusion and observations:
After many change-overs and try-outs, I think that:
1. The lenses available should dictate your choice of camera manufacturer.
2. The way pictures look to you - not the high-tech used - should dictate which camera you should buy. That, and knowing
what you will be mostly shooting.
3. Choose a camera that you love handling, carrying with you, that
feels great, whose shutter sound appeals to you. Not as "airy-fairy" as this sounds...
That's it for the moment. I'll be back with more later. Hope this helps.
A.