I've flown with the i14 a couple of times.
A few hints:
Buy a plastic tarp, and wrap the boat in it before placing in the wheeled stuff bag.
Apply duct tape to the top and bottom edges and corners of the bag. It'll look like hell, but it will avoid friction burn-throughs from the conveyor systems.
The bag will take a beating, but with these extra measures of protection, I've avoided damage to the boat. On my first trip, I went "naked" and did have an abrasion on the boat. In my view, the bag could use just a bit more engineering, or tougher materials, on the perimeter edges...but it'll work.
The actual rolling works well. On JetBlue, they have a flat $75 policy (if I remember correctly) for "windsurfers"...which saves a little on the $50 for oversize, plus $50 for overweight, that you'll pay otherwise.