Wife and I had a date at Swallow in Northern Liberties last Saturday night. Great bistro food, really good, friendly service and good prices (most entrees under $20 which I've found to be unusual among Philly's quality BYOs).
And not one other soul in the place for most of the time we were there. I read reviews in both Citypaper and Phila Weekly before we went and both reviewers said basically the same thing that I'm saying - this is a great value among the newer crop of BYOs but doesn't seem to be pulling customers.
We took a walk around the neighborhood after the meal and saw at least 30 people waiting outside Bar Ferdinand for tables just a block away. Felt sad, especially since we talked to the husband-and-wife team running Swallow after our meal and they were sweet and doing their best to be optimistic about business picking up.
At any rate, I'd recommend folks get out there while it's still open. You'll get a great meal and - if business continues to be as slow as it was last weekend - you'll be treated with the extra warmth and attention that we received.