Considerations when going the custom frame route
I hope some of you can benefit from my mistake.
First, do not pick a one-man shop. If you do, discuss and plan ahead for the possibility that your builder might die or be otherwise permanently incapacitated. That means that your deposit is probably toast. Discuss this before paying!
Second, insist that you receive receipts for any parts delivered for fit on the new frame. Otherwise you have no proof that such parts are yours should you need to recover them for any reason.
I posted earlier regarding T.E.T. Cycles' worrying lack of any communication in the last couple months. This post doesn't mean that the builder is dead. It just means that I wish I'd considered these scenarios before having to go through my experience so far with this particular builder. Bear my experience in mind when commissioning a frame. I don't think many, particularly novice builders, are prepared for this kind of scenario, including putting some kind of continuity plan in place in case if they can't deliver on their commitments and their survivors have to deal with any existing business obligations.
Edit: I removed the last sentence of this post. After some good recent feedback I decided that it was too much. In general, I think the above thoughts are good things to bear in mind for any kind of commissioned work.