Many years ago I got one of the early ones, it was two disc things and you sort of sandpapered the blades.
I followed directions and tried it for a good test, maybe a year? It didn't do much for me and it resides in the drawer of unused notions (a darker place than the isle of misfit toys). I think it can help keep an edge, but it wasn't enough help if you ran over a pin. Pretty much it was I had to start each day/cutting session by sharpening and I just didn't want to do that. If I'm going to take the handle apart, I'm going to just put in a new blade. And then, almost immediately after I run over another pin! Hate that
It took me awhile to adjust my thinking and that while maybe that single unit full priced blade replacement is rather expensive -- but it's a lot cheaper than my fabric and time. I now buy high quality blades in bulk+on sale. I try not to buy fabric or shop online, but when I put in orders for other things on Amazon, I check and see if there are any deals for things like blades or thread or whatever.