And speaking of great glass, Tyson Robichaud reviews one of the greatest pieces of glass available for the Micro Four Thirds system:

The lens housing is built of high quality plastics and metal and while hefty, is not overwhelmingly dense. It feels really good in the hand, and the resistance on both the zoom and focus rings are smooth and responsive, but not too tight. It is certainly large by the micro 4/3 system standards, but I’ve gotten over the “it should be small” point of view long ago and have moved into the, “it can be smaller, while providing comparable quality” camp. I no longer look to the micro 4/3 system as merely a travel system that should be as absolutely small as possible at every turn, no, I like that it CAN be that system when I need it to be, also offering fully professional level tools while being smaller and lighter than the stuff I’ve used in the past.

This is an excellent point. One of the biggest strengths of the MFT system is the reduced size and weight of its bodies and lenses. At first glance, a lens like this looks like it doesn’t belong in the MFT camp, but the system has matured so much over the years that it’s now beginning to offer truly professional-grade glass like the Olympus Pro lenses. These zoom lenses offer everything a professional could ever want: a metal splashproof construction, prime-like sharpness and speed, a retractable hood, you name it.

Mirrorless systems are all about versatility and right now, there’s nothing out there that can beat MFT in that regard.