Hours worked can be very lumpy. At times I have worked very long hours where the project has demanded. At other times I have been able to consistently leave work at 5.30pm.
My work hours change a lot depending on where we are in a project. Toward the end of a project there is often a period where I work very long hours, but we try to make up for that with a lighter time after the deadline has passed. When we aren't busy at work we are very flexible with hours - there is no problem working short days if you aren't busy. I also find that if I need to be out of the office for an appointment or anything that it is no problem to duck out during the day, so long as I'm getting my work done.
Generally, I will leave the office at around 7pm if I'm staffed on a project. If we're leading up to a milestone or presentation, I will work late nights and/or some weekends. In these instances, I find that people are really understanding and appreciative. Another aspect of the culture that I really appreciate is the lack of presentism so if people have finished early, they are free and encouraged to go home. Relative to other consulting firms and other "intensive" professional service firms I would say that PJP is well compensated for the hours we work.