Yeah, QOL has never worked for me in an interview, even w/firms that pride themselves on QOL; many of these firms have inferiority complexes about the quality of the work they do, so I'd emphasize that.
Profits Per Partner is probably about the best inverse measure of QOL you can find. The higher profits per partner, the more they squeeze out of each associate. Unless you're hell-bent on making partner and accumulating as much money as possible, you don't want a high-PPP firm, and if you're in a career so much for the money, you may be better suited to i-banking.
If you're just trying to impress interviewers for this summer, use the buzzwords you find on their website. Some may talk a ton about client service; some may be big on pro bono. If a firm mentions that it gives junior associates a lot of early meaningful experience, definitely hammer on that.
If you're trying to figure out which firm you actually want to work for, you need to ask people who work there if you have any contacts; if you don't, gauge the people you meet at interviews. You're going to be spending a lot of time at the office; probably the most important criteria for long-term success is how happy you are working with the people in the firm. Equally or secondarily important is the nature of the work you're doing; if you're stuck on doc review for several years, that may sour you on lawyering for life.
DISCLAIMER: This post is not legal advice. Alamo disclaims any and all liablity for interview gaffes, disastrous career moves, mid-life crises or other consequences of following the advice given above.