Hey everyone, I'm swaying b/t the 12" and 15" (The $1M Question!)....but also b/t the superdrive or the combo. The SD is only 4X. Is it worth the extra money? The other option is to get an external dvd burner to hook up when I'm back home.... What are your thoughts on whether to get the internal SD? BTW.....how long does it take to burn a full dvd on the 4X? Thanks!