What percentage of bitcoins are being traded/used on a regular basis? Clearly a lot of BTC are being hoarded by either early adopters, or small scale speculators like myself, holding out to see what it's value is in 10 or so years.

What percentage of bitcoins are actually changing hands of a regular basis?
As of October 2012, it was determined that around 78% of all bitcoins minted (as of May 13 2012) were being hoarded "in user accounts that have never participated in outgoing transactions", meaning that all other trading and commerce was actually being transacted with a "float" of the remaining 22% (i.e. less than 1 in 4); and there is really no way of knowing how much of THAT might simply be faux-"trades" between accounts owned by the same entity.

Certainly very little of the total float (and thus even less of the total "coinage") is actually being used as a "currency" to make purchases.