I'm not a µ4/3 fanboy ... but, (the big but), I am hoping to replace my FF cameras with µ4/3. For what I shoot and my expectations the IQ of µ4/3 is fine. What is missing is a native lens system behind the camera of what I'll call pro-quality photojournalist lenses. The wide fast and long fast lenses of Canon and Nikon. In 35mm film FOV, the 200mm & 300mm f/2.8, the 70-200mm f/2.8 and a 16-35mm f/2.8 would make me a very happy camper.
Panasonic has come out with a 12-35mm f2.8, Pre-orders are being taken for the Olympus 75mm f1.8 and I think Oly has announced a 35-100 f/2 and a 60mm macro ... so the long end seems to be covered. Meanwhile I can live with f/4 on the 7-14mm.
PS- As to "must have" lenses ... depends on what you shoot, but for starters the Oly 12mm and 45mm are at the top, toss in Pany-Leica 25 and you have a good start. Pany's 45-200 and the 100-300 are both very sharp. If you need a pancake the Pany 20mm and 14mm both pack a lot of punch for their size.
Kit lenses notwithstanding, the only lens that generally gets panned is the Oly 17mm and occasionally the Pany-Leica 45mm for its tendency to hunt (but it's a macro and macros hunt). At least that's been my observations.