It looks like I accidentally deleted or overwrote my post about OP return. Here's what I think I wrote:

Gavin has had us on his mind lately - at the top of his recent blog post about 0.9 bitcoin software, he talks about explicitly supporting projects like ours with OP_RETURN: https://bitcoinfoundation.org/blog/?p=290

It's looking like we'll have a "class C" transaction type soon. OP_RETURN works very well for our current model of sending transactions from a PC and viewing balances on websites which have the entire transaction history.

Once 0.9 is out and miners are widely supporting OP_RETURN, I think we should start using it.