Personally I'm a big fan of flash, i've built many 'all flash' sites for friends and certain types of businesses .... like you i like the exact positioning and control that only flash can give. That said, it's been a while since we've been asked to create in Flash. Accessibility (much discussed elsewhere on this forum!) and Search Engines have killed much of the demand and popularity.
I'm not actually sure what you mean by ....
If they don't make it to the first page, surely nothing would be logged? Maybe something is implying that the 'Movie' isn't being displayed, in which case i'd say that not all the 15-20% is down to a 'lack' of flash (flash is now 98% accepted). The new version of XP security settings block javascript and active X, both loaded on your frontpage ... this could possibly be adding extra problems (still seems high though).1.) 15-20% of the people who attempt to access my site never make to the first page.
As for ...
This could simply be down to the fact that all the relevent information is contained in the Movie on your index page .. the only 'other' page i can see is the gallery which as you say, is pretty new.2.) 25-30% of the people who make it to the first page never go beyond, and exit instead.
Another possible reason (for both the above) is that much of your traffic could be 'search engines' finding your site from links. In which case they'd register and homepage 'hit' but be unable to load the Movie or follow any of the links to other pages.
I'd definitely recommend developing a HTML version, if only to guarantee inclusion with the search engines.
Good Flash work though