1) I like how great the benefits are, and how amenable my firm is to making sure that I don't totally hate my life (crazy, inconsitent hours and a good work-life balance). But at the same time, I find the stability to be stifling - I'm not opposed to working 14 hours/day if I know that I have a tight deadline coming up, but why do I have to sit at my desk to hit a 40 hour/week deadline if I don't have 40 hours of work to do?
2) I'm currently in a long-term project, and it's the nature of my firm and the projects that my group has that you tend to stick to a project over a fairly "long" time period (1-2 years for consulting might as well be forever). I am doing a lot of self-education during the times during my 40 hours/week that I don't have anything to do, but even so, there's only so much I can do. I've worked on harder projects that taught me more in internships. This is what I'm most dissatisfied with, but I don't want to rock the boat because I want to remain in the good graces of higher-ups.
3-4) My current project is in a field that I have relatively little interest in, and I've found that a lot of the people I am working with want to be lifers - something I DO NOT want to do. I want a creative and diverse (in thought) group of people, and I tend to be in a stagnant place.
Like you say, "working for consultants tends to be a great way to widen the opportuntity surface", but I haven't seen that so far. It may be that I am in the wrong place in my firm, but as I've already said, I don't want to rock the boat and possibly jeopardize the current stable state of affairs, which is significantly better than nothing.