Several things:
Until EVFs have near-nonexistent display lag, correct representation of color and exposure and don't give me headaches and fatigue, my OVF and DSLR are staying.
I don't own it, but the OLED EVF display on Sony's A77, NEX-7 and optional attachment for the NEX-5N/NEX-F3 with its 2 million dot OLED screen is said to be one of the best ever made. So there is a EVF with no lag and accurate colour representation. Optical viewfinder is useless as you don't see what you get and coverage and composition is not 100% and obviously useless for macro. The mirror is great, but removing it is what enables us to get smaller mirrorless camera bodies.
Good optics is what matters, and as of today SLRs (analog and digital) outperform the micro four thirds cameras.
Mirrorless lenses are getting better, the Panasonic zoom with constant f/2.8 for micro 4/3, Carl Zeiss 24/1.8 (yes it's over US$1000) for the NEX system and up coming Sony G lenses seem to be excellent and I'm not sure how SLR lenses are better than mirrorless.
Better yet, you can use a variety of lenses (vintage) on system cameras, although I found really only the NEX with it's 1.5X crop factor to be useful with other lenses, the 2X crop in micro 4/3 creeps wide-angle into telephoto category and the 2.7X crop in Nikon just makes a lot of lenses telephoto ones. Samsung's 1.5X crop is useful but I heard about it being a pain in the backside to use vintage lenses on it (having the mount disassembled? not sure don't quote me).
Just to add Sony, Samsung and Nikon don't make Micro Four Thirds Cameras. Samsung and Sony use APS-C sensors, which are exactly the same size as you get in entry/mid level DSLRs. Just in a smaller package.
There seems to be this misconception by many that the term "mirrorless" and micro 4/3 can be use interchangeably. Many of the mirrorless camera use different sensor:
APS-C with 1.5X crop
Sony NEX, Samsung NX, Fuji X-Pro1
micro 4/3 with 2X crop
Panasonic LUMIX, Olympus PEN
Nikon "CX" with 2.7X crop
Nikon 1
(bit disappointing was going to get this instead of the NEX but the small sensor threw me off)
1/2.3" with (I think about 5.5X crop factor)
Pentax Q, only camera I know to use this point-and-shoot sensor