Pros
Bonneville Power is a part Federal, part Private organization that runs a significant part of the NW power system. As such, it pays "prevailing wage" to contractors and treats their contractors and employees fairly well with benefits, work conditions and opportunities. You have a good probability of working with people that have good backgrounds and are nice to work with, as all employees/contactors are required to have a clear National Agency Clearance Investigation to work there.
Cons
There are lots of "unpublished" policies that can get you fired, for any reason at all, including (if you are a contractor) if someone complains about you for any reason. Two departments near me had people terminated. One for reason (bad attitude), one for no reason that anyone could figure out as he was one of the best people on the team (qualifications and personality). Topping the problem is that no one will tell you what the person had done (even in the most general terms) so that you could avoid the issue as well. This isn't a pro or a con, it just is: if you are into the latest and greatest current technology, this is not the place for you, as they are required to be very diligent about ensuring that ALL systems work with any new technology deployed, whether it is a new type of phone, computer or transmission method.