Pros
independence -freedom to work your own way
Cons
If you are not a permanent employee there is nothing to be gained. They pay invoices late, you need to chase payment, senior management is very sensitive to any perceived criticism. Emails go unanswered for weeks at a time and any complaints about that are then 'your issues'. For example - asking to change a date on a contract 8 times is ignored - then you are gaslit and told you never asked for it to be changed. It's bizarre behavior and the permanent members of staff enable it.
Most agencies take their contractors out for a couple of meals a year to discuss general matters. Here you don't get that, nor anything for xmas or at any other time. They propose a contract with the client for another 12 months without asking you if you want to increase your rate. All in all, it's a pretty poor experience and one I'm glad to have escaped from.