Yes, Flash is of course the biggest problem. Without it I will not be able to use Youtube, Myspace, Facebook and bunch of other main sites that I use frequently. At least not enjoyable at all! The iPad´s web experience is just plain bad experience in this department.
Also there´s other little goodies like being able to have lots of pages open and switch quickly with expose and having the Bookmarks Bar, being able to download files and stuff from websites and so on...
Funnily enough my good man, facebook does work, in fact it works on my ipod touch aswell?
so does youtube.....
not sure about myspace as it is an american thing