I have one, I wouldnt say its the greatest unit personelly.
My first experience was 2 DOA units, but Hema replaced them generally within 1 Business day.
Done a heap of KM's with the Route 66 mapping, only ######ed up once but it was clear it was taking us no where near, we just followed it out of curiosity/killing time anyway.
The 4wd maps are useless, in some areas along NSW coast it was just that pixelated it wasnt useable, and very average in Gippsland Vic.
The Topo maps are simply awesome when 4wd'ing, makes things so much easier.
I wouldnt rely on them for walking though, the battery wouldnt last 2 hours fresh off the charger.