If I wanted "SLR-like" camera, I'd get proper SLR, not Panasonic G or GH model since it's a much comfortable size, it's larger so handles better, it's got better AF ability, it can take cheaper lenses, it's got wider array of lenses and accessories available, I can use it without spending too much battery power so it will last longer before running out of juice (OVF vs EVF) and I can get a weather sealed version (E-5 for instance).
All DSLRs systems are significantly larger and heavier than m4/3 camera systems. As to the power consumption, yes, this is still a disadvantage with not too much relevance most of the time. Just get two spare batteries (which I always had with my DSLRs as welll) and you are done.
If I wanted a high quality compliment for my SLR system, Pens are great - they're small, have pretty good IQ, fantasic OOC results and IS which means lenses are smaller and lighter.
Look at the Panasonic lenses, they aren't much larger. OIS does not contribute much to size and weight (see kit lenses, the PL 45mm macro). Many DSLR owners don't care about OOC because they shoot raw to get the best quality, so OOC is largely overrated, especially as the differences between Panasonic and Olympus aren't that huge and because color rendition is mostly a subjective thing.
I think Panasonic might not get the point of MFT rather than Olympus.
Because you don't the point. m4/3 is not only about miniaturization and retro style (which is getting old by the time), it is
also - not exclusively about smaller camera systems being able to
replace DSLR systems. It is about exploiting live view to the maximum, which can be seen with the new GH2 clearly. With DSLR-like body designs in m4/3 you can have both advantages: DSLR-like operation comfort, and a small size package. The Lumix G system is just at the sweet spot between size and usability, it should not have been smaller, but is small enough to compete against APS-C systems.
When other big players join the mirrorless fight with the lack of current (43rds) ZD glass, MFT is going to lose a lot of customers who want to have just one quality system and of the two, Panasonic will get hit much harder than Olympus because they:
1. Built larger than necessary bodies
They build bodies, which are jsut about right in size and not smallish bodies like NEX, which are difficult to operate.
2. Are pretty generic looking and plasticky - without "soul"
Where is the "soul" of a EPL-1, where is it of a EP-x. Actually I don't need a body with "sould", I need a work horse, which is safe and good to hold, albeit small.
No need for it, if you have OIS. Eventually Panasonic will incorporate IBIS, when the market forces them, IBIS is not an Olympus exclusive asset.
4. Don't have good OOC results for people who want to keep MFT simple and don't want to bother with slaving in front of their PCs developing RAW
Panasonic's OOC results aren't that far off from Olympus', and many enthusiasts love to tweak and print their images in their raw processor, like they did in the darkroom. Raw developing is part of the fun, no pain. If someone likes to stick with the JPEG results baked in by the camera manufacturer's choice of how to implement raw development, you get only half of the things, which digital photography means. Even for quick results, by putting your raw processor on good defaults, you don't mess hours on your PC. You just have to be selective, which images you prepare and which you can just leave of even delete.
Olympus already has an awesome collection of ZD glass which they might easily integrate into MFT line in a couple of years and all that glass easily beats (overpriced) Panasonic mFT lenses which are not weather sealed at all, so pros and people who own expensive zuiko lenses will be able to switch to Olympus mirrorless and have all the benefits of a weather sealed modern mirrorless system with great lenses.
Olympus could have done this right from the start, but still do not reveal clearly, what their strategy is regarding their Zuiko lens line-up. Weatherproof lenses only make sens, when you have a weatherproof m4/3 body - so where is it? It is a joke that Panasonic came up with DSLR like bodies and a good lens line up from the beginning, whereas Olympus jsut did the opposite. Given the companies' legacy one could have expected the opposite. Now, Panasonic has a growing line up of a new lens system, whereas Olympus has a good legacy lens collection (Zuiko) with no prospective camera system for it. I am not sure, if the Zuiko glass can be made m4/3 (= CDAF ready) so easily.
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Thomas