I can only speak for the NY office, but I suspect this is true everywhere.
Jones Day is like a window into what law firms looked like twenty years ago, which will be popular with some and not so popular with others. Most of their work is for old-school, blue chip industrial companies as opposed to exotic financial outfits or the like. They are more formal than most firms, and your personality will decide if that's good or bad. What some see as very polite, professional, respectful, and dignified; others see as rigid, uptight, and hierarchical.
Nice offices, super annoying elevators.
Summered in DC last year. I must say that most of the information about JD in this thread to this point is shockingly accurate for TLS! I particularly agree that what some see as a bug, others see as a feature (and I am in the latter camp in almost every respect about the firm).
As for the "Jones Days, Nights & Weekends" reputation, I think the only reason we have that nickname is because it sounds better than "Skadden Arps Nights & Weekends". Last summer, the office was very busy-- to the point where junior associates were appreciative of taking things off of their plates (rather than worrying about losing hours to the summers), but I never got the sense that people felt overworked, except for those who were in final prep for trial, etc. as would be expected. When leaving for the evening at VERY reasonable hours, the office didn't seem to be abuzz with activity. (Note: this does not account for people who were working from home, or weekends, but it does support those above who noted how pleased people seemed with their quality of life.) If you don't want to work hard, don't go into BigLaw.
As for the atty count in the NJL 350, I was genuinely shocked that the number had fallen. But I wouldn't worry too much about a decrease of 95. That's only 3.8% and that very well could be the result of normal attrition now that the job market is opening up a bit for laterals. (One associate from DC left to go in-house over the summer; another left to clerk for SCOTUS. One partner, sadly, passed away).
A few more things that haven't been discussed in the thread that are noteworthy about the firm.
1. "One Firm Worldwide" is more than just a slogan. And they put their money where their mouth is-- each summer they fly all SAs in North America to a single location for a day of training/seminars and an evening of food/drink to get to know our future peers from other offices.
2. The New Lawyers Group does a similar thing-- only it's a week of training for all first years (and newly arrived second years coming from clerkships). I'm also excited about the prospect of freelancing for several practice areas for a year to find the best fit for me rather than having to hope that the practice area I thought I wanted back during OCI is what I want to do for the rest of my life.
3. Somewhat related to the concern about the smaller NLJ numbers, more than any other firm I interviewed with, JD has a ton of home-grown talent-- especially in big-time leadership positions in the office and the firm. Another telling fact: there are several secretaries who have been there for 20+ years. That type of retention just would not happen in a firm that wasn't a good place to work.
This is already TL;DR. Hope those considering the firm and/or the DC office find this helpful. If you want to post questions, I'll try and get to them-- but it's getting to be crunch-time so it may be a while...