Sailor Ted said:
If I may throw my hat into this ring, I purchased a "D" version of the 21mm CV plastic finder for my then brand new R-D1s for a trip to Hong Kong last November. During that trip the plastic foot broke. I have no recourse for a new finder so I will always opt for more expensive metal-based finders in the future.
This is a bit like the foot for the Vivitar 283 flash which sold in the millions. It had a plastic foot that could break off with a decent whack on the flash. So some aftermarket wizards brought out a very nice metal foot as a replacement. A while after that reports started circulating about people tearing the hot shoe plus prism housings off their SLR's. Plastic feet became more popular again.
I've gone through quite a few finders. I think over the years I must have had about 6 or 8 21mm and 28mm metal finders. Most of them died from slipping out (being pushed) and falling on concrete. The plastic ones bounce. I started putting little 'cap keeper' lanyards on them, especially when I got the 15mm Hologon with its large and hard to replace finder.
I now have various CV finders and Leica, both metal and plastic single focal length finders. The ones I like best are the plastic Leica finders. They don't slip out of the shoes, and are very nice optically. The CV finders are decent, but the plastic ones are higher off the top plate than the Leica ones, and generally show a narrower angle than the Leica ones. The little metal 28/35 is especially poor in this regard, as the 28mm outline is probably about 32mm.
In any case, I'd rather the foot broke off the finder than the top plate getting bent, and probably messing up the rangefinder. Best would be an easily replaceable plastic foot.
The Zeiss finders are very nice, but I've not compared the angles of view to what you actually get. Also, they are too large for my liking, and also of course quite expensive.
The 21/24/28 finder is terrible, and the new vario finder look like an abomination. Maybe it works well, but it sure is ugly. I guess we'll see when they start shipping it.
Henning