My factory fitted system started to swallow my CD's and not return them!! ...... so I had the unit removed and came to the conclusion that seeing it was nearly 10 years old it was better to replace than repair. Besides I mainly played an Ipod through it and stopped using the tape system ages ago.
I went for the Nissan matched Caskia system that is the same size as the original Nissan unit .. Fitted it was approx R12k I had upgraded the speakers a year or two before so those were left unchanged
The system has a whole lot of functionality in one unit, namely
CD player (only one disc at a time- previous unit was 6)
No tape player - no big deal ..IMHO.
Plays DVD's and you can see them on the full colur screen
full Ipod connectivity and the Ipod gets tucked out of site in the cubby
The Ipod functionality is transfered to the unit so you can access playlists etc.
It links to the steering wheel buttons
Has bluetooth phone connectivity with phone book access, caller ID etc.
Has park distance control or rear view camera (extra) _ I chose the PDC
Has built in GPS - A tom tom unit - no extra cost
Has full radio functionality
I think that is it
The positives

Great sound
Nice all in one unit
Phone kit is great
Ipod fuctionality is great
DVD option is nice and can be programmed to leave the screen on when you are driving (if you ask the installer nicely!!) ..... I have not used this yet and obviously will not when driving!
Fills the hole completley from the old unit
could toss my old IPOD connection which was not great.
IPOD use is great as you have all your sounds with you, they dont get damaged in the bush and the shuttle does not jump
The CD player has 30 second buffer to prevent music skip when going offroad ......works well
Radio is good although I hardly ever listen to the radio as IMHO our radio stations are ......... well you know!
Bright screen and good visibility night and day ... the screen can be dimmed or switch off completley in one touch while driving.
Really easy to use ..... I have not had a need to revert to a manual to work the unit.
PDK is nice to have and works well ........ so far

The negatives

The GPS is about as useful as an ashtray on a motor bike!! ..... especially offroad ........ The first time I used it on road , it tried to take me on wild goose chase that would have added another 60km to a 150km route!!! ...... have not investigated this further.
The touch screen functionality is not that easy to use for some functionality - like selecting songs from a playlist etc.
It does come with a stylis which helps this a bit
It would be better if the unit was placed higher up in the dash as you cannot tilt the screen and some of the stuff at the very top of the screen is not visible from the driver position.
Some of the text on the screen is a little difficult to read (I use reading glasses) ... I drive with prescription sunglasses .... this solves this problem.
The price!!
Cheers
Steve