I have to agree, I always use 800x600 and that is 
on a 17" monitor.  I am fairly nearsighted but 
even most of the customers on the helpdesk I 
support use 800x600. I'd bet a lot of people 
don't even have larger than a 15" monitor- think 
about the fact that many of your customers are 
college students, and colleges don't usually buy 
large monitors for their labs.
As for flash- I don't like it. Granted my site is 
way out of date as far as how it looks (heh, I'm 
starting to figure out dreamweaver so we'll 
see..) but at least it always loads, and you 
don't have to download anything.