I've got one. It will handle 16" blades. I've not done blades that long, but the instructions indicate that it will hold blades that long.
As to using it, i'm really glad i have it. I've got both the stock wheel and a course green wheel for it. I was genuinely surprised and a bit ticked the last time i had my blades sharpened. They came back with a lot of material removed and had what i'd consider to be a rough surface on the beveled edge.
Now i only take off what i need to, and the stock wheel really gives a smooth flat finish on the steel. It's easy to use and works well.
I've never used a Tormek type of wet grinder, but the Makita suites my needs and cost much less.
Paul Hubbman