I need your thoughts on this.
First of all, you really have to keep an open mind regarding all brands and styles of cameras. All too often many folks keep themselves confined to a brand - as if some sort of brand loyalty was needed and to do otherwise would amount to heresy.
I shoot with a variety of different camera types (and brands) and each brand something really nice to the table.
I've been shooting with the G series since the G1 and have loved them all. By the same token, I also shoot with various DSLR's and Micro 4/3 cameras.
But what's important to note is that you shouldn't assume that you can only have one or the other. Heck, I'm a firm believer of having several (if not more). Keep that G-12 as it's a fantastic camera platform, but add to it and get that micro 4/3 camera that you might be looking at - you won't be disappointed. The only thing that you will notice is that the menu scenarios - as they're different - but it takes just a few minutes to adjust.
My micro 4/3 cameras currently include the awesome (older) Panasonic GF-1 and GH-1, along with the wonderful Olympus EP-2. These are fun cameras to shoot and they have superb IQ capabilities - yet they're not huge cameras, so you still have the lightness factor. I really like the format and it's taken off big time. I'd love to eventually get that OM-D model, but there are waiting lists for that one.
As for getting a micro 4/3 camera, I'd strongly suggest getting the E-PL3 model since it has an articulating screen and more controls on the camera itself.
But in getting back to the G12, I'm still amazed at how good it does to this day and I use it often when I want to bring something along without having to lug tons of accessories with it. Ditto that also for my Nikon P7100, the Olympus XZ-1, and Panasonic LX-5 - all superb camera platforms!