m4/3 are making allot of new products. They are getting some fast primes coming and some fast zooms.
But I have olympus epl-1 with the vf2 and that is my travel package most of the time. The thing is very compact, and the lenses I have are smaller then my canon setup, with equally good iq. But the m4/3 like all camera has it's limits. Shoot within them, and you will have excellent results. Get out of their operational envelope and you will have very poor results.
m4/3 does not have the evf refresh rate to keep form blacking out between shots, and they do not have the AF system to shoot any serious action. The GH2 has the best AF for a m4/3 but you really need to work it to get action shots.
What they do super well for is long reaching shots. The 2x crop gives their 300mm zoom 600mm of reach. They also shoot excellent general photography stuff and macro. And the olympus has wireless ttl so you can work with off camera flash. Besides using olympus and panasonic 4/3 ttl flashes, metz and nissin has 4/3 flash options that are very good.
Their lenses are getting there, as they can use 4/3 lenses with adapter, you can get the 30 1.4 for the olympus and it will work on the epl-1. It just focus slower. And sigma said they are going to join m4/3 so allot of the sigma lenses may get m4/3 mount in the future. So is schenider and cz of others.
And unlike aps-c, you can get a excellent megazoom lens for m4/3 giving you excellent reach in a all in 1. The lenses does not have to have as big a image circle, and with the crop factor the olympus 14-150 lens is 300mm of reach and is very sharp unlike allot of the 18-200 lenses out there.
So if you know how to use the system, and need a compact system, m4/3 is a very good choice. And you will have allot of more lens option vs sony and samsung currently.
So I do not think m4/3 is a fad. It has developed into it's own segment of the market, no longer a niche. And it is a good compliment to a dslr when you need something smaller. Just accept less DR and 1600iso as the top, though the new ones can be push to 3200iso. It still does not match a t2i at that iso.
Traveling is my passion, so I am a major Frequent Flyer.
Canon 60D, T1i/500D, Eos 1, Eos 630, and Olympus epl-1. Current Canon Lenses ef 100 2.8, ef 85 1.8, ef 50 1.4, ef 28 1.8, ef 50 1.8,ef 28-135, ef 70-300, ef-s 18-55, ef-s 55-250, 500D close up lens. Current Olympus lenses oly m4/3 14-42, oly 4/3 35mm 3.5 macro with m4/3 adapter, panasonic 45-200, panasonic 20 1.7. And a Part time Pentax K-X shooter.