Pros
Great compensation, great benefits, good people with competent leadership. For a software engineer, Boeing is a good place to grow as a leader managing complexity, but technical growth is limited to very specific facets of the defense industry. The work is somewhat interesting/enjoyable, and there are opportunities to present advances to the company and industry. Social ambition (offering to manage projects, presenting, running meetings, etc) is rewarded greatly, and technical ambition is rewarded only with breakthroughs, patents, etc.
Cons
In St. Louis, the location is pretty awful - in a bad area of town and older, dreary office buildings. My biggest complaint is that the company is so large and there are so many technical problems being solved, that there is a ton of redundancy. You might be working on a solution for a year, only to find that another team has implemented something very similar. Joining the solutions may be technically or politically difficult, so then each team attempts to justify its pursuit of the solution. Technical competence is rewarded differently by different teams, and to truly stand out, I recommend joining an advanced technology organization like Phantom Works - this gives you the opportunity to work on more interesting DARPA projects and to pursue patents. While leadership is generally competent, the overall management system at Boeing is overly complex and it can be very frustrating.