I know what you mean about the difference in framing on an RF. It's nice to see outside the frame lines, but at the same time, its sometimes nice to see the crop on an SLR.
You guys talked me into it. I found a good price on a Summarit 90mm so I think I'm going to jump on it. It'll save me from buying a 135/2 for my Canon, which I'd then probably never use.
I'm really tempted by the Leica 90 Macro lens - if I could find it at a good price, I'd seriously consider it. The extra bit of close focusing distance (without the adapter) is tempting, as is its collapsed size. Perfect lens for keeping in the bag on a trip and pulling it out when you want to focus in on a detail, either close or far away.