I had zero interest in the previous M cameras, simply because none of them had built-in view finder, electronic or optical, and the feature set was pretty spartan with a lackluster sensor to boot. I care not much the lenses, as I would be using manual focus lenses most of the time anyway, but it is always nice to have the option of auto focus lenses, especially primes. The M line has no fast primes, except the 22mm f2, which I heard is actually quite a nice lens and is affordable. Canon has many low cost and excellent primes for the EF line, and those can be used with an adapter that supports full AF operations, but then again, mounting those on the M with an adapter would make it look bulky.
One of the aspects of this camera that slightly interests me, is the improved sensor. The dual pixel AF should speed up the focus speed considerably compared to previous M bodies, but I would not expect it to be even comparable to the newest mirrorless cameras from Fuji, Olympus, Panasonic, or Sony. If the sensor in the 5D Mark IV is any indication, the one used on the M5 should have similar performances in terms of noise and dynamic range, which is definitely a step up from previous Canon sensors.
The downside? It's not full frame. I am not a full frame snob. I still have the APS-C NEX-6, two M4/3 cameras, and now a Nikon 1 V1 with a one-inch sensor, but I have gotten so used to the look of full frame sensor that I use it most of the time. I wish Canon would produce a full frame Mirrorless using current sensor technology.
So yeah, I won't be getting the M5, but it's getting interesting. The build is definitely more robust than previous Ms and hopefully, this one will become the entry level model, and a more upscale, full frame M1 [note the missing 1 in the M line, reserved for the top of the line model :)] is in the works.
Blossom - Canon 35mm f3.5 from Prima Point & Shoot & Sony A7.