You have probably worked all this out, enduro, but for others reading this thread....
Yes, the download is detailed - it is the complete set of 1:50,000 maps of NZ. LINZ is Land Information New Zealand (ie the government's land management statutory body). LINZ have made all this mapping data available for no charge - free ! Wouldn't it be great is each state in Australia did the same?
They haven't been updated since Oct 2013 (a major system crash, I believe) but this will only result in minor differences with the current LINZ maps (geographical features don't tend to move a lot - although NZ does have the occasional earthquake). If you want to compare current with the download, go to
http://www.topomap.co.nzThey have DOC tramping tracks (mostly) but additional track data can be found at
http://www.routeguides.co.nz and
http://www.tramper.nz