Oh, I see. I wasn't aware that it was also available in stores, but since it is, that changes everything. I was hoping to find figures on how many copies were sold over Steam, thinking that it was the only way to get it.
As awesome as Ep1 was (while it lasted), I had the impression - thinking that it was only available over Steam - that Valve was too afraid to release such a short expansion pack in stores. When I buy a game in stores, I automatically trust that it's going to be longer than 5 hours, but when I download it over Steam, I'm ready for anything, and nothing surprises me.