I have a 10". My opinion is they work, and they will cut a side off fast. How much flesh you leave on the carcass is basically in direct proportion to how fast you go. If you filet Alaska style and leave a fair amount of flesh on the carcass, but aren't worried about it, they're great. Use caution, you could do a whole lot of damage to yourself with one if you aren't careful.

Mine sits in the drawer, not precision enough for me. I use my $25 folding Kershaw 99% of the time.