I got a new Nexus 7 last week and most useful apps so far are
Maps with Me (download detailed offline streetmaps for most countries)
Gtasks, Evernote, Dropbox, Pocket
Guardian, 1Page BBC News, Google Currents, Zite, Reader
Tunein Radio, TV Guide, SBMX(sketching app)
Bus scout, National Rail
Various ebook readers, still trying these out but have managed to borrow an ebook from the library with the OverDrive Media app, this could be very useful.
Tuner - Gstrings free (chromatic tuner, works fine for fiddle!)
I am still looking for equivalent of Apple apps Tunebook and GoodReader, haven't found anything to replace these yet,nor an easy way to download mp3s from Internet Archive.