Yes, to play or record or copy HDV material you either need two HDV cameras or a computer with HDV editing software and one HDV camera.
HDV data takes the sama space as miniDV, 13 GB/h. That's because they both use same tapes and tape mechanism and certainly try to maximise the quality the system and medium can provide. HDV is packed about 4 times tighter, though, with long GOP MPEG2 compression, miniDV is compressed by frame and not nearly as much.
When editing HDV it is usefull to convert the HDV data into a frame based codec (Cineform, Apple Intermediate Codec or the like) to make editing easier and faster and to minimize intermediate rendering artefacts. This means the HDD space needed for one hour of HDV using these codecs is about 35 GB/h, not 13 GB/h.