When I bought my M8 it was after having an RD-1 for a while with Zeiss 28 ZM, 50 ZM and CV 90.
I subsequently purchased Leica 28 Summicron, 75 Summicron, which in turn led to a perilous downward spiral of CV 15, CV 12, 21 ZM, CV 35/1.2, Leica WATE, Leica 135/3.4 Telyt APO, Leica 90 Summicron, 35 Summicron, Noctilux and now most recently a 50 Summilux.
Overall I think that Leica have benefitted quite well from the M8 with respect to lenses. It's also fair to say that both Zeiss and Voigtlander are doing well too, with the added market of the Epson in addition to the traditional film cameras.
The good news is that I've yet to have a bad rangefinder lens experience with any of the vendors.
If Zeiss could find a way to have their lenses coded without the need for hand coding or milled replacement flanges from JLM etc then I could easil have been a 100% Zeiss customer. Convenience/bother/UV/IR optimization eventually lured me to all Leica lenses now (with the exception of my CV 35/1.2 and 12).
The quality of the Zeiss lenses did however have an impact on my DSLR lens buying habits and so I'm now a big fan of the ZF lenses (18, 25/2.8, 35/2, 50/2).