I recently picked up a Lumix GF1 at a good price and while I like it very much - it strikes me as the best of this crop of M4/3 cameras, like all small cameras without an inbuilt VF - I found that composing (or worse yet, focussing when using a legacy lens) can be very near impossible when using the LCD in bright sunlight.
I tried taking photos in the sun on a yacht on the weekend and had to guess composition as the LCD was effectively blank because of reflections. This is a common problem and I dislike this aspect of small camera shooting.
Fortunately I have a collection of older optical finders of various sorts (fixed focal length and variable) that I used with my Leica M and LTM cameras and tried a couple of those in a quick trial the other evening.
With a 28mm lens (leica M mount and adapter) on an M4/3 camera the field of view is close enough to a "standard" 50mm lens so I tried a Voightlander "Turnit" finder that was originally built for a Voightlander Prominent rangefinder of the 1950s. Although it has a bulky rectangular design it has good optics as well as a range of focal lengths - 35mm/50mm/100mm. The 100mm should work well with a 50mm lens on the M4/3 just as the 50mm works pretty well with the 28mm lens I was using . Another finder I have is the 75mm finder (came with the Voigtlander 75mm f1.8) which should be good for a 35mm lens on the m4/3.
I thought it worked well. The main hitch was that it sat quite loosely in the hot shoe and could not be left there permanently for fear of it dropping out. I suppose I could shim it with a piece of paper / plastic or some such........At the other end of the spectrum, another finder I tried was too tight and could not be used for the opposite reason - once on I would never get it off. I find this is common with many old accessory finders - they seem not to be wholly standardised to the size of the hotshoe / accessory shoe and vary enough to require some tweaking. Modern ones are a better as they are more standardised in this respect, but are more expensive option.
I have a couple of old generic brand bright line finders that I may also try next weekend. I did have time to try one of these but its optics were old and degraded so looking through it was nearly as bad as looking at the LCD in bright light. This is another potential issue with old finders.
If you are using a range of lenses on the camera, possibly the best old finder to use (assuming it foot fits the shoe on your camera - I have not tried) is a variable finder with focal lengths from 28 - 200 by a German company named TEWE. These come up on eBay from time to time at various prices. Without something like this you need to buy individual finders to match each len's focal length.
http://www.rockycameras.com/accesso...l-length-frame-finder--nice--2499-19157-p.asp
Turret finders also work but these sit high above the lens and parallax can be a problem - and they look odd.
http://fedka.com/catalog/product_info.php?products_id=331
My conclusion is that optical finders work well on digital cameras if the optics are clear (although not solving the manual focussing issue, only the composition issue ) so long as you can find one that is of suitable field of view and also remember to allow for parallax if shooting at a close subject.
I know you say that you do not want an electronic VF but they have come down in price if you hunt around (I can get one for the Lumix at around $130 plus shipping.) If you do not have any accessory finders like me, and have to buy several to match various lenses at the end of the day this may be cheaper and could still be worth considering notwithstanding your objections to them.