Gps
The GPS unit in my 550 is just crap, did not know where Charters Towers was, tells me to turn right but shows left, gets stuck in a loop going round in circles, turns where there are none, maps 10+ years out of date. And I think everyone that actually uses it has complained but the dealers can do nothing. There is/was an upgrade map but $450 or so - no thanks.
I had Northfield car sound (Brisbane) fit an additional unit to provide different (common) GPS program plus Hema maps. It's not cheap. So now I have the choice of 3, Nissan/vanilla/Hema, and upgrade is cheap. To replace in dash unit completely means losing other options on the display, but this add on is transparent. U have to load the alternates that's all.
Next big innovation will be using your mobile phone for 'free' gps via the indash unit - can't wait but it's not gonna be tomorrow!!