The SL is really quite tempting to me. I use an M240 and a Sony A7II with the Voigtlander close up adapter. I shoot a lot of shallow depth of field - I have the Canon 50mm 0.95 with rangefinder coupling (converted to M mount) and a 80mm 1.4 R among my lenses.
The EVF is required to get accurate focus of the 50mm on the M240, but I very much value the automatic zoom that the rangefinder couple provides when I move the focus ring. However, images are normally better from the Sony - probably because of the higher resolution EVF and the better implementation of the focus peaking.
I really don't use the rangefinder mechanism much, for street work I zone focus and shoot stealthily from the hip (although with practice I have become pretty good at nailing around f 1.4 @ 50mm at the 3m distance mark) but the general portability and form factor stealth of the M remains attractive. I also think that it's old school looks adds a degree of stealth / acceptance in street work.
My other lenses are 21mm f1.8 (Voigtlander), 28mm f/2.8 (Zeiss), 50mm Nikkor f1.4 LTM and a couple of Jupiters (35mm and 85mm). Also, I have the Zeiss 55mm f1.8 AF for the Sony (but never use it).
Having the two cameras is useful when owning only prime lenses, I'll often have both with different focal lengths mounted for portrait and model work.
As I write this out, it seems like the logical thing would be to stay with my current two bodies but that SL EVF still calls to me... Also, there's the rejuvenation factor - investing in any new kit has a satisfying disruptive effect on my work, a rekindling of creative intent and renewed motivation to shoot.
The SL feels like the right camera for me, but can it compete with the sum of the two cameras I currently own. A purchase of the SL would require the sale of both.
A dilemma.