When Episode 1 came out, my daughter wanted to start watching. I told her she needed to watch 4, 5 and 6 first (although she didn't).
I think anyone who doesn't watch them in the order in which they were produced might end up missing a lot because the technology to create these movies is so different. So while Episode 1 is a prequeal (SP?) it's got better technology and graphics than episode 4 which happens afterwards.
Ah well, we'll see what 7 has to offer us.