I'm pleased about that, I'm pleased about your success, I'm pleased about what has happened, I'm pleased about moving house
I'm pleased with you, I'm pleased with your work, I'm pleased with the result
It looks like 'with' might be more common with 'static' objects and 'about' seems more common when referring to more complicated 'events'. I'm sure there's a better grammatical explanation out there!
Looking forward to something = sich AUF etwas freuen.
Being happy about something = sich über etwas freuen.
So if the sentence were: "Die Leute freuen sich darauf", it would mean "The people look forward to it". Otherwise it means they are currently happy about something.
[edit: Too slow :D]
I will use "about" with a situation, "with" for a product review, and "for" to express empathy with a human.
- The deadline was just extended and I'm really happy about that.
- Jeremy just got a new job and I'm super happy for him!
- My new frying pan just arrived in the mail and I'm happy with it!