We definitely saw an impact at www.tradeking.com. However, the impact (negative) was delayed and appears to be isolated to a few head ("primary") non-branded keywords. We saw traffic begin to decline on these keywords on March 3rd. So, it seems like we were impacted more by post-Panda "tweaks" than by the Panda update.
Moreover, our Google ranking for one of these primiary keywords dropped from 5th to 11th (now 12th) on March 3. Even more interesting: said keyword had held steady at 5 or 6 since the Vince update. Prior to the Vince update, our ranking for that keyword had been around 8 or 9 (with some fluctuation). Effectively, our Vince gains have been lost (for this keyword) and we've lost a few more positions on top of that. Could that be a clue?