Jay, there is a rather long thread on this forum about my struggles to get my 445 running right. If I'd had the option of the timing set and cover I'd have been really happy to be able to change cam timing a few times to get it right. As it was, removing the timing set required dropping the oil pan and removing the rad, then pulling the cover, balancer and gears. All told cost me about 10 hours of work. Now I know there are guys on here who can do it in 2 hours, but I'd never done it before, and dropping the pan with the engine in the truck was complicated. Getting it all sealed again was much more difficult than when it was on the stand in the first place.
Once I had it apart I didn't have the option of changing the timing and trying it, then advancing it some more and trying it again. Once it was buttoned up that was it. Now I'm happy that it is running well, but I wish I'd had the option of trying different positions. BTW it would be REALLY cool to be able to do it on a dyno.
In retrospect I would rather it wasn't almost $500, but I wish I'd had it. For what it is worth the Ford timing set was around $100, so the spend would have been an extra $400. In an odd way it may be worth more to an inexperienced builder than an old hand.