The social aspects of Hubpages will help with Google rankings (comments, etc.), but the Panda update only changed an estimated 2% of search results as I have heard, so the difference really shouldn't be drastic.
As far as trying to find out - you might want to check the traffic value? Its a little over 1.5 million right now, but I never looked at it prior to the update so I can't say either way.
The subdomains that HP is now giving to everyone probably made a much larger difference than the Panda update ever did.
Panda should help HubPages overall, but don't credit all positive traffic change to the update as it might have just been you.