The advantage, of course, is that you have access to DVD features not normally available over streaming. The methodology is what Zediva believes will help them out in a lawsuit brought against them by the MPAA earlier this week.  The MPAA, as you might have guessed, sees things a little differently.  They call the site's streaming plan an attempt to "rely on technical gimmicks in an effort to avoid complying with U.S. Copyright Law." 

Registration is still closed on Zediva, but the company says that more people will be allowed access as soon as possible.