DCA - pleasant staff. Can get crowded. Bartender is not always around when you want a drink. Nice views and easy access to gates. Food selection is standard.
ORD - self-service bar. Nice amount of space. Room with a TV, but the chairs are not too comfortable. Food selection is standard.
JFK T3 - since putting in the purchase food area, the complimentary offerings are on a table that is otherwise hidden. However, the SCs at JFK are like a zoo. I haven't been to the oasis lounge, which I hear is nicer.
LGA - have only been to the one after security, which is a dump. Needs renovation. However, food is standard, and it's easy access to the gates.
TPA - vurry vurry nice SC. Sunny and comfortable. Nice staff. Food is standard.
LAS - oh that's right. LAS doesn't have a SC. DL needs to put one in ASAP.
Third party lounges in BOM / DEL - total dumps, extremely crowded (all foreign carriers use a common lounge in those two cities). Hot, indian snacks, however, are delicious.