I am a little late to this conversation, but I thought I would throw in my two cents. I discovered Spiderweb through Exile II on a shareware disk, what feels like ages ago, but was probably about 12 years ago. I have been a huge fan of all of the Spiderweb games since then.
I just wanted to make a comment about BoA's poor sales, Thuryl's opinion that it was due to the registration barrier, and Yama's response that the registration barrier was the same for BoE. If I remember correctly, the registration barrier for BoE was NOT the same; you could play all three of the built-in scenarios without registering, you just couldn't play other scenarios or create your own. Playing through all three scenarios gave me a good appreciation of the range of scenarios that were possible, both to play, and to create, and contributed to my decision to purchase.
The lure of Spiderweb games has always been the depth of gameplay that is available before buying the game. Whenever I start a Spiderweb demo, I do it knowing that by the time I reach the registration barrier, I am going to be so immersed in the game that I won't be able to stop myself from buying it. And that's ok, because I am never disappointed. BoE accomplished the same thing, even though it used three different scenarios and no cliffhanger; the draw was what was possible when other people started creating their own scenarios.
Unfortunately, I was disappointed with the quality of scenarios that came out for BoE. There were a few good ones, but nothing that I felt matched the quality of the games built by Spiderweb; and there were a LOT of bad ones, too. This was not terribly surprising; most of the scenario developers were "amateurs", without the benefit of JV's experience. Still, it left a sour taste in my mouth.
Similarly with trying to create my own scenarios; I found it very difficult to do even the simplest things. Especially as a programmer myself, I became frustrated quickly at the lack of basic constructs that I am used to using to express my intent. This is not wholly JV's fault; building an editor to process complex decision trees (without using a flexible scripting engine, as he tried to do with BoA) is a difficult task, and I don't think the result was bad given the effort he was able to put into it. But it meant that I was never able to bring my ideas to life the way that I had hoped I would be able to.
BoA didn't even have the benefit of three scenarios to draw people in before registration. VoDT was not bad, but that by itself didn't have the cliffhanger effect that Spiderweb has proven is so effective at driving sales. Combined with my own bad experience with BoE, BoA became the only Spiderweb game that I have never purchased, and don't plan to.
All that said, I am planning on looking at BoE's source code now that it has been released. I doubt I will do much if anything with it; but its always a thrill to take a peek behind the curtain