I'm trying to find a reason NOT to do this:
Sell: 5D2, TS-E 24/3.5L II, 24-105/4L, 40/2.8
Buy: Oly OM-D, Oly 12/2, Pan/Leica 25/1.4, Oly 75/1.8
Size, weight, price and general flexibility seem to outweigh the advantages of an all-out DSLR system. I'm finding you have to dig pretty deep to find significant differences in IQ in practical use. Has anyone made this kind of change?
I have both a 5DII and an m43 (Panasonic GF2). But my 5DII glass includes 35mm f/1.4, 50mm f/1.4, Sigma 85mm f/1.4 and 135mm f/2. There isn't any equivalent on m43. The GF2 (with the 20mm f/1.7, Olympus 45mm f/1.8 and occasionally an adapted canon 50mm f/1.4 or 35mm f/2) is a nice compact camera (and movie mode works very nicely on it)
However, ISO can't really be cranked up high, AF isn't as fast, doesn't feel as snappy over all, the built in flash is nice but doesn't compare to the 430EX I use on the 5DII. The glass is nice (and I can adapt my canon lenses) but the FF sensor really takes it up a level.
Much like the advice I give on Canon bodies, I'd recommend against buying the atest and greatest m43. They seem to run on very short product life cycles, so you can buy an older model for peanuts (and then buy the OM-D for peanuts a year from now).
Same applies though to a lesser extent to the m43 glass -- the brand new lenses tend to sell at a premium because there are always a handful of people who are prepared to eat a $100 or so premium for the shiniest toy. If you're interested in dabbling in m43, my advice would be to pick up an older body and don't get sucked into buying the just released lenses yet.
I have to disagree elflord on this one.
I own both the 5D II w/ 35 L, 24-105L and my baby the 70-200 II and the OM-D E-M5 (25 1.4, 12-35 2.8 and 45 1.8 ). The only comprable M43rd camera would be the GH2 and only in Video. The OMD is a better stills camera than the GH2 by a mile
Regarding AF speed and accuracy, the OM-D easily bests the 5D II for single exposures, but it does lack in focus tracking/servo performance.
As far as the glass is concerned, the higher end lenses are cheaper than L glass, rightfully so given their proportions. The glass is just as sharp though, and the optics are much easier to produce given the smaller sensor. The M43 Glass (specifically the Pani Leica 25 1.4 and the 12-35 2.8, and i expect the Oly 75 1.8 ) is easily comparable to the 35 L (which I own) and the 24-70 L mark I. In fact I would say that at wide open apertures, the 25 is considerably sharper than the 35 L. Also the DOF on M43 at 25mm 1.4 is still very shallow, and I would say more usable than a 50mm 1.4 on a FF camera (m43rd crop factor is 2x)
ISO is almost as good as 5D II, very comfortable shooting at 1600 and 3200 in a pinch. The biggest change with the OM-D is the RAW file quality is awesome. so much headroom for highlight / lowlight recover and better dynamic range than the 5D II.
The 5D is still better for large print pixel peeping and m43 still does not have a native 70-200 L Mark II equivalent (soon to be released 35-100x2.8 ), but I find my 5D spending a lot of time on the shelf these days.
I would also say the IQ on the OM-D is easily usable for professional use outside of large scale printing.
I do agree though it is probably worth waiting for Photokina