It's the best 24mm lens you could possibly put on your M8 (but not by much). Because it is a retrofocus lens (similar to SLR lenses), it's better suited to a digital sensor in the corners than the Zeiss Biogon ZM 25mm f/2.8 (which I would much rather use on film, but which some believe performs equally or even better than the Leica 24mm ASPH when it comes to evenness across the frame).
The 24mm f/1.4 Summilux might be better in some parameters of image quality, and has f/1.4 light-gathering power, but is ludicrously expenive, and has comparatively high levels of distortion. It's also gigantic by comparison, no longer enjoying the advantages of the rangefinder philosophy.
There's really not nothing much more to say, the 24mm f/2.8 is one of Leica's best performing lenses - if the fact that Erwin Puts consistently uses it to prove maximum resolution figures on slow-speed microfilm is anything to by, at least.
If you ever upgrade to a film Leica M or an M9, you'll have to get an annoying external finder (and an SLR will really start to look appealing, i.e. an Olympus OM with a 24mm f/2.0 is smaller, with close focusing and accurate framing), but on your M8, you can use the built-in 24mm frame lines.
Enjoy it!