There will always be a gap between what can be done with various size sensors (physics never takes a day off) but how it manifests itself depends on what you're expecting from the camera.
My LX3 experience has been that at low ISOs I can get acceptable enough results to leave the slr at home, so long as I'm not aiming to make big prints or heavily crop the images or shoot action or very low light (or shoot subjects unsuitable for the zoom range). But the roughly 4x larger imager area my dslrs give me provide a much wider performance envelope that can be seen in cleaner image detail, lower noise, greater dynamic range, and higher ISO range, not to mention the ability to shoot much shallower DOFs. (Noting the actual image pixel count is basically the same.) Can't ignore the speed differences either--compacts are very poky in focusing, shutter lag, file write times, etc.
The GF3 and E-PM1 are so tiny that with a pancake lens, they are nearly the same size and weight of an advanced compact and performance-wise, will outperform all compacts lacking a big sensor (a very short list). This is a pretty new development that makes them a viable option for anybody looking for a very good small backpacking camera.
Still, within a fairly narrow performance window any of the latest high-end compacts will get close enough to still warrant consideration. And the old saying about any camera you have being better than one sitting at home still applies.
In sum, there are inescapable advantages to the µ4/3 options but how you use the camera dictates how often you'll run into them. I'll add that ergonomics play a role because using a camera on the go places a premium on a camera that fits well in your hand, is easy to compose with and has the controls you want in the right place.