Sigma 35mm f/1.4 DG HSM, reviewed by drmaxx

Is the focusing pretty reliable?

Yes

Focusing is reasonably fast and very reliable. In very low light (e.g. indoors, low illumination) it has some issues with finding a focus fast - but nothing I wouldn't encounter on my 60D with other lenses - e.g. the Canon 50/1.4.

There was quite some buzz about some lenses having a their focus point off. My lens is without adjustments quite accurate. On the picture below I am maybe 50 cm away and focus on the face of the baby in the manger. You can see that my lens has a little backfocus - although the focus point is still in focus. However, this also just could be me wobbling (this was taken handheld) - I did not make any systematic tests as the lens satisfies my needs.
P.S. To give you a size reference: The holy 'spikes' are about 1 inch.

Can you compare it to any of the 35mm by Canon or Nixon?

Sorry, don't have any of them. But here is a recent thread that are discussing some of the issues:
Sigma 35mm 1.4, Did I miss something?