It's usually great seeing old friends. You don't have to plan what to say, watch your words, suffer awkward silences, or try to guide and manipulate the conversation to where you want it to go as you might with a client or a workmate or even, frankly, a partner when there are chores to be allocated or holiday destinations decided.
With old friends, you just turn up, crap on and see who can make the other laugh first. If you say something that comes out wrong, they're not going to judge you.