My family bought one when I was in my teens, nearly 15 years later and it's found it's way to my place. Still going strong. For a bit of surf fitness, it would probably be pretty decent for building stamina and muscle tone in your shoulders and arms using an extended arm pull down in the prone position. You'd have to be on it for a while belting out lots of reps though. Resistance is pretty low, and my work requirements leaned more towards the need for strength for short periods of time (I'm probably the worst paddler in Perth), so I outgrew it pretty quickly. For surf training, it would probably be pretty helpful if you were willing to put in the time to make up for the lack of resistance with high reps. But then you'd probably be better off going for a swim or a surf anyway.
All this said, I'll still jump on it in front of the TV if I can't make it into the gym. The kids enjoy jumping on it to add a bit of extra resistance too.

If you just want paddle fitness you can do it MUCH more cheaply.

You can set up an old tyre with a couple of lines with handles, one of them passing through a pulley tied to a post.
Lie on a bench in paddle position and pull the tyre backwards and forwards. You have to lift the front of the bench up to keep your hands off the ground. Use a small tyre and adjust the resistance by putting bricks in it as required. Low profile tyres are cool but deep ones hold more bricks.

It works all your paddling muscles, neck, shoulders, arms and has that cool ghetto vibe that everybody loves.

I wouldn't buy anything that puts a dollar in Norris's pocket. Nasty man.

Went back to my trusted workout and thought why spend the cash. Why is chuck a nasty bloke. I always thought he was cool.