Venus Rising, are there other character flaws you don't tolerate in your friends? Telling them off so roundly for being any more than 5 minutes late sounds a bit high maintenance. But I guess if they come back for more you must be worth it. 
Interesting correlations with some of what is described here, and ADHD traits, particularly with those people exhibiting inattentive strain type deficit disorders. Those perfect people who are never late may not empathise, but the anxieties as described by cruikshank, and conversely, the daydreamy, easily distracted ADD behaviours can be a real barrier to getting out of the door in a timely fashion.
My closest friend and I are very different personality types. One of us is a motivated, high achieving, controlling, perfectionist neat freak who arrives early for everything. The other is lazy by inclination, able but less driven, calm, disorganised and not as punctual. Our friendship has survived almost 30 years because we recognise that our positive character traits each have a flip side - which can drive the other crazy - but that with some consideration we can try and meet in the middle. And we realise that neither of us hold the moral high ground for being more inclined to one set of behaviours than the other.
peacoat, I really empathise with you as to how frustrating your DP's behaviour must be, but when you say this lateness is a deal breaker do you mean you would end the relationship over it? As a pp said upthread, does he have compensating qualities which balance this out? Anyway, I'm glad he has listened to you, and that you had a better weekend. It sounds like you can empathise with the effort it takes him to be punctual, and that he is able to appreciate how his lack of time management impacts on you. Good luck, hope things continue to improve.