Pros
Good people who take the time to mentor. Good diversity of security work (low level, back end, webapp, mobile). Exciting deeper security research work as well which can keep you interested if you want to back off the day to day security audit worktrain. Among consulting companies Leviathan has the best reputation among local security consultancies and is the right size where as an employee you get lots of individual attention and help.
Cons
Downsides of Leviathan are like any consulting company, its possible to get in a rut of doing the same type of security work week in and week out. This is one of leviathans strengths is that they actively pursue not just the dollar but interesting gigs to keep stretching people as employees and keep things fresh.