I purchased the product after browsing the TOC and available sections on the semi-wiki. So having it available did influence my purchasing decision.
It could be useful for online browsing but even on a high bandwith connection I notice enough delays to make it less than appealing for me to use during a game. But it is fine for casual browsing while online if i need to maybe check something and i don't have the NOVUS book handy.
A user wiki would be nice too - where folks could add bits of information about house rules, tables, classes etc. But I'd imagine controlling that sort of thing would be a logistical nightmare.