Just been to have a look at what the PEN is all about, and the MICRO 4'3rds thing.
Nice piece of marketing, making out that the lens circle to sensor size is the important thing. NO IT ISN'T, THE SIZE OF THE SENSOR IS THE IMPORTANT THING.
When I read the first few posts I was interested, I thought, aha, a rangefinder with full frame sensor....just the job. Using a retro name to set the photography world alight again. Then you read into it a bit more, and realise they are using an APS sized sensor, the same as everyone else - they have just cleverly described it differently.
Nope, I won't be selling my G10 to get one of those. The G10 offers wider coverage and longer coverage, without changing lenses. The output files are about the same though. I am very happy with the lens on the G10, I don't like the 400 and above ISO performance - it is dire to say the least. If you need more than 200, forget the G10, it is AWEFUL. If you can use it on 80 or 100, then it is great and the lens coating actually has a very high contrast if the light is sidelit - almost polarised effect (only doesn't cut out glare like a tre polariser). For the wide use I put it to, it is fine. I have had plenty of DPS published form it, so it is doing OK. Faster to use than the change of lenses.
Plus, would the cost of changing be recouped by extra sales? NO. So I shall use the money I have just saved to do another trip instead.