Pros: diverse work force, decent hours
Cons: hierarchical, no job/salary advancement, unwieldy, unstrategic
The ACLU has a tremendous reputation and has achieved some truly amazing milestones/victories in the fight for civil liberties over nearly 100 years.
If you're a lawyer, this is a great place to work, but if you have other skills - policy, communications, digital, advocacy - look elsewhere.
The lawyers have an iron fist hold on all decisions related to strategy including decisions outside of their skill set. Management is terrified of the legal staff and will not push back, so skilled professionals who are not working on litigation or direct lobbying have to yield to illogical non-strategic "tactics" designed by lawyers who have no knowledge of (or real interest in) the wide range of opportunities that move public opinion around civil liberties. Good ideas are met with bullying from the lawyers to implement their ideas instead.
I've not yet met a lawyer who doesn't love it here- so if that is your field by all means apply. But if you are not a lawyer and want to flourish in your field while also working on behalf of the issues that matter most then this is not the place for you