I like those, but I can't afford a big self-healing mat, or at least I wouldn't use it enough to justify the expense.
The rotary cutter I have is the Skil Power Cutter.

And apparently I got it super-cheap. I paid about $20 at Lowes when it was on sale, but right now it looks like you can't get it for less than $40 new or $30 refurbished. Still, the ZipSnip is an unknown, whereas Skil is fairly respectable, and the Skil one is lithium-ion and definitely rugged enough to survive being dropped a few times.
Mine's pretty handy for cutting big pieces of cardboard to smaller sizes, cutting thick plastic (like garbage-can plastic), metal screening, etc. Much more powerful than regular electric scissors, but you'd have to try hard to cut yourself.