TLRs are nice, but getting used to shooting that way can be difficult to get used to. Then again, it can also be a source of inspiration.
I have a Mamiya 645 Pro, and I'd recommend it. The plastic body is light and as portable as any other MF system, the 645 aspect ratio gets you more shots per roll without reloading, and I feel it gives me the best of both worlds as far as image quality vs. portability. You can add or take away prisms and winders to balance size and convenience. It has an electronic shutter, like most modern cameras, but battery like is extremely long in the camera.