I've got this one, in Rokinon brand, as my 'normal' prime on my 7D.
Firstly, image quality is amazing, use bryan's comparison tool, or search for an old thread of mine where i took samples and compared it to my efs 15-85 (it easily beat the zoom).
Raw image quality (resolution) is practically the same as the Zeiss 35/1.4, they beat the canon L in the corners by a long way, in the centres at smaller apertures all 3 of those lenses beat current sensors.

But the aperture is octagonal (only noticeable above f/5.6, and then it's not that noticeable because everything's in focus). Just don't use it as a macro lens.
And at f/1.4 there's a bit of a loss of contrast, stopped down past f/2 and the lens is perfect.

Build quality is good, better than an ef-s kit zoom, but not up to L or Zeiss standards. It doesn't focus past infinity, sometimes getting just to the exact point of infinity is hard (depends on air temperature and other things). Mine was bought second-hand with a focussing problem, I fixed it but maybe the problem getting to infinity is because of that, not by design. Also, there's a slight delay when you focus in one direction, stop, and focus the other direction (again, could just be my copy).
It's about as big as the canon L, not exactly your small walkaround lens, but I think it's lighter.

I've given up focussing it using the standard viewfinder, I always use live-view for manual-focus lenses (and i've even glued an AF confirm chip on my samyang 35). I just got an email today to say my KatzEye split-prism screen has been shipped, maybe viewfinder focussing is better with that. But if your viewfinder is too dark once you stop down, just try to get used to focussing with open-aperture then stopping down before taking the shot (like in the old film days).
De-clicking the aperture takes all of 5 minutes with one screwdriver, which is what i've done.

I'm sure i've got images floating around the net for examples, but i'm on my work pc on the road so i can find samples later.

But in short: It's $400 or so. The canon L is $1400. The Zeiss is $1800. If they're your options, I'd choose the Samyang every time, I can put up with Manual Focus and non-Tank construction to save a grand or more, and you can't beat the IQ.
For the same price as the Sigma 30/1.4, the sigma gives AF, the samyang gives FF. The sigma is smaller, the samyang gives much better IQ, especially in the corners. The samyang also has half the CA of the sigma. Between these two you'll have to decide which are the more important factors.