Matt:
I'll add a few thoughts to your comments, since I mentioned buying plans in my reply to your message in the SOF Canoe thread.

-Most builders are unwilling to admit that they've spent a lot of time building a 'dud' boat, so the reviews of homebuilt boats tend to be uniformly positive.
-In fact, most owners-not just builders- are unwilling to 'bad mouth' their boats - look at the paddling.net reviews for data on that.
-A lot of builders seem to be 'just getting into' paddling, so may not have a great deal of 'seat time' in other (professionally designed?) boats to use as comparison.
-Aside from the CLC and Pygmy boat reviews in the now-defunct SeaKayaker magazine, I don't recall reading reviews by expert paddlers of many plans aimed at home & hobby builders. So buying plans is no particular protection or assurance that I'll get a great design, in all cases.
-If the boat is used in benign conditions - paddling along the beach with the kids, or on a quiet river, most designs will do the job.
-I tend to have more confidence in designs by people that are 'known (at least to me) good paddlers'. For instance, I wouldn't hesitate to build a Petrel or a Siskiwit kayak. Bjorn Thomasson's designs are in the same category, and I have built one of his designs that I like a lot, so I don't think twice about buying designs from him.
-It's not that I'm very busy, or very poor, but I value my time and don't like to waste materials, so spending $100 to get what I think will be a good design doesn't seem excessive. Much above that number, I do get more particular. ;-)