I don't think the Leica R lenses get much respect, especially for adapting. Like I said before, they are big and heavy.
But I think they are decent quality, and built to a pretty high standard.
Since I don't have experience with your lens, I can't say. If it is a decent price within the range of other good quality manual 135's, and in good shape, it should be a good buy.
Others you could look at that get some praise are the Takumars. You can find 135 and 200mm ones in different apertures.