I had a worse experience with EVFs at the time of the Dimage7... I couldn't use it much more than the back screen because it wasn't bright enough (or not enough shielded from external light), but it was some time ago.
And yes, I'm much more inclined towards the LX3 or another "serious" compact for bulk & weight reasons. The G1 is smaller than my 300d but not that smaller - and it would mean reinvest in a complete system. I keep an eye on the new µ4/3 Olympus though, when it will be more than a block of wood.
I've never tried an EVF before. From what I read from others, this is very unlike any EVF ever before. Its very bright all the time--but you can also do a display that shows you exacctly what you will get with a particular shutter speed--esp. useful for manual.
There are M mount adaptors for the G1. Cameraquest has one as well as Rayqual, Novoflex--and there are probably some on ebay. Check this charthttp://docs.google.com/Doc?id=dx428wg_10fdvsmtd7
Its constantly being updated as more and more appear. I believe Jim Milich has an M also. I bought the FD adaptor from Cameraquest http://cameraquest.com/adp_micro_43.htm
To use MF assist with an MF lens, you go into the menu and choose 'shoot w/o lens'. I would say all of us are just leaving this on as it doesn't seem to make any difference when using the Panny native lenses for AF at all (BTW, you can use MF assist by setting it on dial on camera top left and just touching the focus ring on the Panny AF lens also).
With the MF lens mounted with its adaptor, you can just MF with focus ring, but to use MF assist (10X zoom), you click on the <- of the 4 way button which brings up the large MF square. You can reduce the focus square size to smaller by using the front dial. You can also move the AF square to anywhere except very far edges of image. Then click on OK (middle button of 4 way) and you get a full VF of 10X zoom and focus with your front focus ring. It takes quite a bit longer to type this than it does to use it LOL. Most of us are using aperture priority, letting the camera choose the shutter speed--and often using auto ISO letting it choose ISO.
Hope this explains sufficiently. For anyone wanting to shoot with alternative lenses of all but EOS (AFAIK), there are probably straight adaptors or in some cases, using 2 adaptors (though many of these will be supplanted with direct adaptors as these cheaper adaptor mfg. offer them). I owned one old 50 f/1.8 which I think was a kit lens for AE-1--I just kept it so I had something on the body. I looked around, saw that the FD lenses were good on the G1, bought an adaptor, bought a 24 f/2.8 and 35 f/2.8 (would have liked faster but plan to buy Panasonic 20 f/1.7 this Fall when its out and these were smaller than faster in same FL), a set of 12mm, 20mm, 36mm and added a 25mm extension tube set (those for $20 total) and I have a nice MF set in FL range I normally shoot for under $250. And--its fun to use. I still have my 5D with a lot of EF mount lenses, but I find I'm carrying the G1 quite a lot.