Out of interest what problems are you having? I'm also in NZ.
I am using the HDHomeRun DVB-T and the problems I am having is when I go on TV3 it does not decrypt the signal. I have looked at nvidia driver and all but was told that Mythtv 0.22 is not so cool with the H.264 codex. It is working ok on TV1 and TV2 just take about 1min to start displaying the channel. but if you go to TV3 it dies. Then Have to go out of Myth go back in a few time and then TV3 sort of gets better.
Andrew told me to that Myth 0.23 fix a lot of this problem and also has about a 15% increase on the H.264 codex from what I read on Mythtv's release notes..
Are you having any problems?