I'm strongly considering putting Keelshield on my boat. This topic came up of alternatives when someone suggested Keel-X from the folks that do Line-X in their truck beds.
The protection from scratches and small dings are there, but the cushion provided by the Keelguard and Keelshield products are not duplicated with these other options.
I like the idea of not being able to see the coating like the product mentioned above. But if your keel nails a rock or underwater obstruction, you may need some shock protection to avoid the major fiberglass damage as well as the gelcoat. A combination of the film with KeelShield down the middle may provide the perfect solution.
Good luck!