Meh, I don't know why people get their panties into such a bunch about punctuality. There are some things I've always said I would NEVER be late for:
1) Crew (when I did rowing; 5am sharp, every day, all year, 4 years)
2) Work (unless I accidentally slept in, which very rarely happened)
3) School papers/presentations (unless there was a dire emergency and I had to ask for an extension, but again that is a rarety)
4) Church (when I used to go)
5) One-on-one meetings (e.g. coffee with a friend)
6) Medical appointments
7) My own wedding
(yes, that was actually something that's been in my head for a long time... that's one event I will NOT procrastinate on, or be late to)
On the other hand, things I am willing to be 5-30+ mins late on:
1) Social occasions with more than one person
2) Classes (I try to avoid it, but it does happen)
3) Going to bed
4) Going anywhere when I'm having sex
When other people are late, I take a little chill pill and don't let it bother me. If they are REALLY late (as in, 30-60+ mins), then I start to get irritated, but forgive them if they call to let me know what's going on. What PISSES ME OFF is when someone is late, and then calls (or doesn't call!) to fricking CANCEL the whole thing. That really drives me nuts. I set aside a time for you, gave you grace when you were late, and now you cancel on me? Total flakedom. No mercy.