Scott Bourne posted a mini review about Canon’s flagship Speedlite, the 600EX-RT. Synthetic and concise, the review discusses its features, also compared to previous versions of Canon’s Speedlites. Quoting:
The main thing I like about this flash (other than its amazing power) is it’s ability to zoom from 20-200mm with a Canon lens and to do so automatically. This is quite an improvement over the 580EXII and if I were to buy the 600, that’s the main reason I would do so. The built-in radio control is also a big deal since it eliminates the need to buy third-party flash triggers.
Btw, the 600 EX-RT is suitable for Canon Instant Double Rebates if bought together with a 5D Mark III, 5D Mark II, EOS 60D or EOS 7D. The Instant Double Rebates apply to the mentioned camera bodies and selected lenses and/or Speedlites. Savings can go up to $250, depending by the kit you choose. The rebates last until June 2.