It seems to me that the official guide data is not as accurate as would be liked; particularly for the shorter listings. WHile you can extend by 10mins and cover most things it messes up if you want to record two programs following each other. Most of my experience is with recording programs for the small children, which tend to be short, frequently repeated, and episodic.

My analysis of it would be -

TV1, TV6, TV7 - Very accurate, broadcasts start within 1min of scheduled time. Lots of detail on episode data. Thumbs up for TVNZ.

TV2 - seems to be broadcast about 4-5min later than scheduled. I need to have an extra 4min or 'extend' enabled for recordings to be sure of catching the end, and then it messes up following recordings.

TV3 - seems to be broadcast about 3-4 minutes earlier than scheduled, which is even more problematic as you can't easily start recordings early. Also, several programs appear to be missing the episode data so we end up recording duplicates - particularly since TV3+1 causes the program to be recorded again 1hr later if the episode data is not there.

CTV8 - Missing episodic data completely, as it is probably not being provided by CTV at all.

Prime, MaoriTV - Missing entirely, of course.

I havent bothered with Parliament TV and the radio channels yet.