I feel that for someone to claim they are entitled to all th advantages of BigLaw while working Mid- and Small- Law hours is an indictment of our current culture.
Do Mid/Small Law firm associates work/bill less hours? I don't know if that is true. I think they bill for much less, and therefore make much less, but tend to have the same workload as the Big Firm associates. Also, I would argue that working for a Big Firm can actually be much easier than working for a small/mid size firm. Big firms have more help staff around to lend you a hand on projects; word processing centers, copying vendors on site, tons of secretaries, paralegals, and project assistants to jump in and help out.
Also, it has been my experience that if my hours are written off, I am still credited with them on my monthly reports. The client is always haggling with our partners (Jones Day). Often the client will ask for a break on certain things and our partners are inclined to grant them concessions on the bill in order to keep them happy. I still get my credits for the hours.