I'm undecided on this one....
I 'launched' my site pretty much as soon as Apachie (webserver software) was installed... but I keep a blog on the front page informing people of the goings on.
As I have a forum there, it gives users more of a sence of community.... that's probably the wrong word to use under current circumstances, but you get my drift
People have joined the forum and got to see different aspects of stusplace come and go. They also get to sudgest stuff for the site.
All in all, I think it's ok to promote an un-finished site, but not to leave it that way!
Too many peoples sites say stuff like "I'm updating this site" or "I'll be adding more soon" but nothing changes for weeks on end.