I think that some of the commentaries here are a bit unfair to the AirSpace Lounge. One thing to bear in mind is that the BWI lounge is their first effort and one they'll hopefully learn from as they move forward.
It's been quite some time since I've used the lounge, even though I'm in the D Pier regularly on UA. Ended up at the lounge not too long after they opened when I had a 5 hour flight delay. Decided that the $17.50 (at the time) was worth it for several hours wait.
From what I recall, the food and amenities were decent. UA charges $50 for a day pass to the United Club and that's completely pathetic when compared to lounge offerings by SAS, LH, VS, SQ, etc. I hate to use such a low standard as a comparison, but this is America - and we do crappy on our lounges. With that in mind, the AirSpace lounge is a deal.