As I stated in my introduction post, I'm currently using a Nikon DSLR, but my plan for the near future is to move toward the m4/5 system, and I've found that maybe Panasonic GF1 (or even GF2) can be a good choice for me. I had some quick trials and I found it really comfortable.
The reasons why am I thinking to do this can be several: light and smart equipment, good image quality, a very interesting range of lenses, a camera system that makes me concentrate more on imaging and vision than on gear settings, the evolution of an open standard that seem to become a landmark in the next photographic future, and so on. It's also very easy to foresee that the future of cameras is mirrorless.
However, I am still a bit concerned on the quality performance I will be able to obtain, comparing Lumix GF1(2) to, say, Nikon D90 - or similar entry DSLR.
The main issues are noise and prints. I'm not concerned with high ISO (>800) or extremely demanding situations, but with normal shooting cases: daylight, landscapes, street, portraits, etc.
In particular, my personal FAQ about m4/3 is: will I still be able, once stepped into the m4/3 world, to obtain good 20:30 cm or even 60:90 prints?
Do you have any experience to tell? I've read that some of you are previous DSLR users, or that some of you use a mirrorless camera as a backup for more advanced systems. What's your opinion?
I'd like to add a follow-up question to yours, which will hopefully be answered soon. In addition to noise/printability, could someone address the responsiveness of a M43 camera like the GH2 in comparison to a DSLR? Do you have to deal with things like shutter lag or delays which essentially are not present in a DSLR? I was thinking about getting a D7000, but the latest images made with the new Panny 100-300 lens are really making me reconsider.
JC, I have tried a GF1 myself and I haven't noticed any alarming shutter lag, the responsivity it had was just fine as I'm used to with my D90 - but I must tell you that I've not tried the GF1 in particularly demanding situations because I could handle it for a short time only.
The FPS rate is way slower than in a medium level DSLR, but if you don't need extremely fast series of shots (I don't mind, for example) you can forget it.
My favourite photography, a part sketches of holidays and family, is urban, street and landscape. For these genera, in particular street and urban, a m4/3 can be a real killer, not only for its reduced dimensions.
It's also very likely that in the near future (next 2-4 years) we will see some giant-steps improvements in the m4/3 and mirrorless field. All major companies have joined or are joining this format, including commercial monsters like Canon and Nikon - also for this reason I'm so confidend that m4/3 can be a good choice right now.
I would back everything Roger said and add a little from slightly more play time with the GF1. I am coming from a Leica R8 so my SLR background is a little different, too.
I got surprisingly good street and landscape photos up to 43x32 cm at 240 pixels to the inch bearing in mind that (1) I only used RAW and (2) it is easy to bracket RAW automatically. Even the sometime maligned 800 ISO produced grainy but otherwise usable photos. The latitude of the sensor allows you to recover +/-2 EV.
I also used my R8 lenses on the GF1. The ergonomics are such that the Summicron 90mm (180mm on the GF1) is really only a tripod lens but the 50mm (100mm on the GF1) can be hand held in good light. Used this way, the photographs are stunning! The sensor is capable of great things with a classy lens in front of it.