I've been using it since well before 2009 and have built a kayak or canoe designed with Kayak Foundry every year since 2003.
As well as the 15 designs I have built, I have dozens of other designs created just for fun.
I have created sea kayaks, a TK1, two K1s, a Tc1 and a C1, so it is more versatile than you might expect for such an easy program.
The fact that it limits the degree of control reduces the work and increases the chances of a design being fairly smooth.
One big difference between KF and other CAD programs is that KF starts a new design with a sea kayak already on the page, so all you have to do is modify it to suit. ou don't have to start from scratch.
It is free. It works. It is easy ti learn. There is a lot of help available on the forum. What more could you want?