I have a couple (sorta - see below) and I use them occasionally, but mostly I power-sand with a drill, because I find it works better for me. I do find doing the bottom of a bowl difficult with the inertia sanders because the bowl isn't really moving in the center, so there's little to drive the sander. Basically just hand-sanding there, except with an inconvenient sandpaper holder. Your mileage may vary.
The inertia sanders I use are just cheap mini die-grinders from Harbor Freight. Just the grinder, no air hookup. Don't know how they perform as grinders, but they spin good for inertia sanding. I have a straight and a 90 degree - I think they set me back about $9 each.
To avoid the annoying spiral on the bottom of a bowl when power-sanding, I stop the lathe and do the bottom with a sort of random motion.