Pros
Generally, employees have a fair amount of autonomy, and the pay and benefits are not bad for many positions. Employees seem to be friendly, although many are fairly introverted. The location is, I think, pretty good, given that it is right in the middle of Capitol Hill, and the buildings are some of the most beautiful in DC.
Cons
Unfortunately, LOC needs a lot of improvement. While employees have a fair amount of autonomy, this appears to often be a result of lack of management and oversight rather than an effort to encourage creativity. Also, many employees abuse their autonomy by not doing much. Management often looks away from employees' bad behavior, so some employees do very little work while some do a lot of work with no apparent discernment among management with regard to pay or advancement based on merit. People seem to often move up pay-wise and position-wise based on time in service. Also, upper management appears to change quite a lot for reasons that are often unclear. Personally, I think my pay and benefits are pretty good, but I have heard many complaints about pay from other employees. The impression I get is that the majority of LOC employees are between GS-9 and GS-12, but I don't really know for sure, and I don't know how that compares to other federal agencies. LOC provides little, if any, professional development. An employee organization does provide $300 in support for education for certain classes, but I have not heard of a single person receiving financial support to take professional development or graduate school courses. Finally, LOC seems to be unwilling to make significant changes to procedures, policies, etc.