I took my 7" tablet with built-in GPS and Oruxmaps installed to NZ on a recent walk. I had LINZ topo maps and DEM files installed for offline use. The LINZ topo maps were from: https://sites.google.com/site/irnzmaps/
It performed fantastically. And now with Garmin's recent December 2015 firmware update on the Oregon 6xx series, I can now preplan trips on the large touchscreen android device to create a GPX trail and copy that to the microsd of the Garmin GPS.
The advantage of the bigger 7" screen was fantastic, and my tablet's quick GPS reception was a plus. It was great as a backup to paper maps. I also have the Garmin NZ topo maps, but found that the trails on the LINZ maps were much more accurate than the Au/NZ V4 Garmin Topo Maps.
Also once I downloaded the DEM files, it gives a good 3D preview of the day's walk, which was pretty neat. The Garmin Oregon also does a 3D with DEM files, but it is so slow in comparison to OruxMaps on the Android tablet.
I met a french guy at Bog Inn Hut who was doing the TA trail. The day I walked with him, he just clocked his 1000km mark. He had a Sony Xperia and Oruxmaps, but no topo maps only the very basic OSM map, so I put his MicroSD card into my tablet, copied the LINZ topo maps across to his card as well as the DEM files, and voila, now he had the topo maps to refer to as well.
I only had the North Island on my tablet, but gave him the link to download the South Island maps when he had wifi.