oxnsox: You've gotta laugh at the wording on the coverage checker. It appears the options for coverage are either 'Likely' or 'Unlikely'.
Now excuse the pedant in me, but the word 'Unlikely' implies that there may be some possibility... in an optimistic way its a word full of hope, and just a little bit of tease. Where in some places its actually very very easy to give a definitive 'No bloody way mate'.
Soo... here I sit in sunny Nelson optimistically wondering if I add a few dozen more elements to a yagi or find a taller telephone pole to mount it on then I just might get some HD before 2013... ok it's unlikely, but........
I think you'll find that the chances of HD in Nelson are pretty much 100%. The coverage map on the freeview website has it pretty much covered here: http://www.freeviewnz.tv/images/uploads/pdfs/Nelson.pdf
Both Kaka Hill and Mt Campbell covered by September... lucky you!!