For DC: http://opm.gov/oca/09tables/pdf/DCB.pdf
You max out at just above 150k, but it would take you several years to get there because you start at step 1, then go up a step each year. At year 4, it seems fairly routine to get your 15. I do know someone who has been denied a merit scale increase for several years, but that was someone who was clearly shooting himself in the foot time after time. However, you can get small bonuses, although I am not sure whether they count towards the max (I've heard that they do not).
My impression was that about half of honors hires end up staying in DOJ. For my agency job it seemed about the same, except people tend to leave more often before their tenure is up. You definitely feel a bit more security, but there is immense pressure to perform at the DOJ and very high standards, so it doesn't really make any difference in how you go about life. Screwing up is a big deal, and there is more on the line than just your job- prosecutorial misconduct is your worst nightmare. For the agency job, since it is an administrative court, it seems like less of a nightmare. Also, people do tend to rest easy after a couple years and get closer to working only the 40 hours a week. My agency job was unionized-now that was job security.
People do a lot of things after the DOJ. To me, it seems to give the most options of anything. State and Federal judges; other local, state, or federal positions, sometimes politically oriented; private practice is wide open; and there are some very specific things you can do depending on what your litigation was in. Obviously, you can go to general litigation, but white collar criminal defense is said to be hiring big right now because Obama, it has been said in some law periodicals I've read, to be expected to increase prosecutions. There really isn't much out of the question from DOJ, except some transactional work I suppose.
From the agencies, where you can go will depend on what you do. They definitely go to other government agencies, including DOJ. They also end up being a lot more specialized, in employment law or environmental law or tax for example, so they can end up doing more transactional or in-house work. When people leave those jobs it tends to be because they have this huge brain in some special area that most people don't understand. Sometimes, you are the person who actually wrote the regulations on a statute. I've seen people from my agency go into transactional work as well as litigation in private practice, although I will admit that not everyone has the creds to do it. It really depends a lot on what you do and what kind of special projects you can get on in these agencies to obtain the specialized knowledge and stand out a bit. There is definitely a sense that people who work in the agencies can be little more than government employees with no potential for much else, but the stars definitely have opportunities.
I don't know much about federal defender jobs. There is definitely respect for many who work in it from the government side, but I am unsure of what their lifestyle or pay is like, or what kind of mobility they have professionally.
-OP (edited to add this)