I own the big Sony Flash, and have done an in-store comparison against the standard Sony Flash, that came with my Nex3. The Big Flash was easily 2X-3X more powerful, so quite useful for me. It does pull more power from the battery, but not bad at all. The quality of light is outstanding. No redeye, nice built-in diffuser and bounce.
Worth having IMO.
“The secret of getting ahead is getting started.”
― Mark Twain