If you're going to stick with one system, then you made the right choice. I have the E-P1 to go along with my K20D (which is now a K5). My Pentax setup is much more extensive and I can get pretty much any shot I want with it.
The Pen is my "Point and shoot", and to that end, it's great. Plus, I can add some older manual Pentax lenses to get shots like this one from a B52s concert:
Which leads me to an advantage of MFT (at least cameras like the Pen and the GF series from Panasonic) - they don't look like dSLRs, or "professional cameras". At this concert, no way could I have gotten my dSLR into the show, but a little camera like the Pen is obviously not a "professional" camera, so it gets into places like that.
Here's my totally scientific
scale to compare point and shoot cameras, MFT, and dSLRs:
cheapo p&S---------G12, S95----------------------------------------------------MFT----APS-C
I have the Canon G9, and I gave it to my wife about 1 day after getting the E-P1. To me, it's a lot better. Unless space is absolutely limited, I like MFT better than a P&S. Currently, you can get an older MFT model for less than many top P&S cameras (the E-PL1 kit is $399 at Fry's, probably cheaper online). If you can swing it, MFT is a great compliment to a good dSLR kit.