well, as a precursur - I'm involved with this project so I am biased!
The S-1000 will surely be something a pretty select group of people will be really interested in - that much is a given. IC's came along and the world of analog synthesis stabilized, pretty much relegating tube based synthesis to some almost lost history books. It's an arcane, and arguable method of synthesis to say the least - but just like people hunt for Arps and Moogs and Rolands for various characters, filter types, etc, some people will instantly feel a sense of intrigue at the concept of an all-tube synthesizer.
Here's a link to some of Eric's (Metasonix) schematics and a brief write up on some history of tube synthesis -
http://www.blaze.net.au/~sasami/synth/tube/ it's fascinating stuff even if the usability of the synthesis is entirely up to the individual.
Personally, I'm so freaking excited to see this thing released. It's in prototype form now for various reasons - mostly due to the nature of the board, wiring, powersupply, and the panel logistics. He wanted to display the prototype at this stage so people would see what he was up to. It's going to be a very different synth, and it's to be expected that the cost, the sound, and the niche nature of the product will create a pretty small audience.
milkman- to address a couple of your points: as far as tracking and stability, he's getting the tubes to track and remain stable quite well. The range isn't as high as other osc methods, but it's remarkably stable - check out his specs on that link.
As for "warm" etc - that's not so much the concern, I mean certainly with tubes there will be an expected tone to the overall timbre of the machine, but warmth is not really one of the selling points
This is a lab for unheard sounds, and at it's core is a bit of nostalgia to interact with synthesis as it could of been had the IC not been invented.
/michael