There's a lot of information in this thread already but, for what it's worth, I'll add my contribution. I considered the 12-100 for a long time, thinking that a single lens covering that focal length range would be ideal for general, walk-around photography. Eventually I bought one and took it on holiday to try it out properly. When I got back home I returned the lens for a full refund.
The problem was, I found it too big and too heavy to be comfortable. It felt like one of the full frame lenses I changed to M4/3rds to get away from; and because it covers such a range of focal lengths you don't tend to take an alternative lens with you to give some respite. It wasn't too bad when shooting, and the lens was supported in the hand, but when walking around it hung down and swung about like a pendulum! I would say, try the 12-100 if you can before purchasing.
It was quite a relief to go back to my usual duo, the Olympus 12-40 f2.8 and the Lumix 35-100 f2.8. The Lumix lens is a superb optic: fairly small and light, very sharp, Dual 2 stabilisation with Lumix cameras, and the barrel doesn't extend when zooming, so it stays very compact.
Since my experience with the 12-100 I've actually purchased the Olympus 40-150 f2.8. Yes, I know, it's even bigger and heavier than the 12-100, but I keep it for more specialised photography, such as wildlife in the garden or close ups etc. For those purposes it's an excellent lens, and I'm prepared to put up with it's size and weight.
The problem was, I found it too big and too heavy to be comfortable. It felt like one of the full frame lenses I changed to M4/3rds to get away from; and because it covers such a range of focal lengths you don't tend to take an alternative lens with you to give some respite. It wasn't too bad when shooting, and the lens was supported in the hand, but when walking around it hung down and swung about like a pendulum! I would say, try the 12-100 if you can before purchasing.
It was quite a relief to go back to my usual duo, the Olympus 12-40 f2.8 and the Lumix 35-100 f2.8. The Lumix lens is a superb optic: fairly small and light, very sharp, Dual 2 stabilisation with Lumix cameras, and the barrel doesn't extend when zooming, so it stays very compact.
Since my experience with the 12-100 I've actually purchased the Olympus 40-150 f2.8. Yes, I know, it's even bigger and heavier than the 12-100, but I keep it for more specialised photography, such as wildlife in the garden or close ups etc. For those purposes it's an excellent lens, and I'm prepared to put up with it's size and weight.