I used a spike to punch holes in my early leather projects, that's an awl for you purists. I switched to a sewing awl at some point.
When I'm hand-stitching, I use a stitching awl to poke my holes. The tool I use is this one from Tandy. I took the spool of thread off and just use the tool for punching holes. I never liked the stitching awl and lock-thread method. The thread they use on the spool is too thin for my tastes and is non-waxed. Plus, lock-threads are messy and hard to do by hand. All the local saddlemakers I know use the two-needle "saddle stitch" method, and having done it for several years now, I agree with them. So my stitching awl is used only as a glorified leather punch. But the needle is the right size for my holes in order to pass both needles (I use glover's needles) through without too much fuss, while not being too large a hole for a sloppy stitch. The rounded handle on the awl makes it comfortable for pressing down through the leather. But then again, I mostly work with 4-5 ounce leather at a minimum, which is thicker than most of you use for sporrans.

When I started making sporrans I bought a rotary punch and boy was that a good decision! I bought the cheapest one Tandy sells and it still saved me bunches of time and frustration. It was under $20 and worth every penny.
If you're talking about one like this, I agree. I have one in my tack room that I've used for as long as I can remember for repairing saddles, bridles, etc. Those things are a 'must-have' tool for anyone who works with leather! I don't care for them much, though, when trying to build nice-looking pieces because I prefer to use a hammer-type punch on a flat surface where I can be a bit more precise on my hole pattern. I build a lot of custom gun leather items (mostly rifle buttstock wraps with lots of punched holes for lacing and such, rifle slings, etc.); my layout is critical and the 'angle of attack' needs to be just so. But for everyday hole-punching, I agree that the rotary punches are very handy and useful.