Dredging this back up from the ancient past...especially interested in whether anyone's using the "MATE" 28-35-50/4 Tri-Elmar on a camera more recent than a G1 and whether you think it's worthwhile.
Well.. it comes to personal preference then...
and since you already have the lens, I would simply drop a few bucks (check ebay: rainbowimaging for example) and try it out.
I personally prefer how my summarits and summilux lenses at those focal lengths render over the MATE (whether on my M8, M9, or Micro 4 3) . I found the MATE nice for the convenience of 3 focal lengths back when I was shooting with just one camera... Epson R-D1 (and M6). 28mm at wide open was a bit too soft for my taste.
That's helpful and interesting - which version Summilux? I'm assuming not the ASPH?
I have Summilux ASPH @ 50mm (summarit and noctilux f/1 too)
At 35mm focal length, I have an older summicron 35mm (which doesn't get used much) and a Summarit 35mm
At the 28mm focal length, I had the 28mm elmarit (partially funded when I sold the MATE). I later sold it for the 24mm Elmarit Asph which I am totally happy with.
The MATE is a jewel of mechanical wonder... part of the reason why I regret selling it. It is one of the most complicated lens ever designed out of Leica. It also provides a great package for a 1 lens 1 camera kit for street photography. On the other hand, its rendering didn't set it apart from the Summicron's and Summilux's that Leica is well known for. None of this really translates to an advantage on the micro 4/3 camera. Also, with the 2x crop its fairly limited on the micro 4/3 sensor with f/4 as yet another limit to work within. The WATE actually provides a better set of focal lengths on a 2x sensor. I think you could do better with some of the high value native lenses out there; 14mm, 20mm, and you already have the 45mm. But again, its preference and an M mount adapter is fairly cheap to buy to try it out and decide for yourself.
PS> I see you have a 90mm f/2 APO. Nice! I should have jumped on it several years ago prior to Leica prices skyrocketing....