Plus:
3D perspective view
Better graphics
Heaps faster
Did I say heaps? Lightening fast!
Can read dual-layer DVDs
Easy to customise
Less bugs, more reliable

Q: 1. Will it be TMC enabled or does the MKIV need an additional upgrade for that?

A: Mk4 is always TMC enabled. No changes needed.
but you will need map disc that supports TMC, and radio that has the TMC receiver built in.

Q: 2. Is the screen I have 4:3 or 16:9, is there a way to tell?

A: To tell - look at it! But all Minis have widescreen.

Q: 3. Will I be able to retrofit bluetooth and an ipod connector once I upgrade to a MKIV (currently not possible due to having a CD changer; it's either an ipod, bluetooth or CD changer with my Mini).

A: Cd changer does not exclude bluetooth. Bluetooth is an easy add-on.
To have iPod + CD changer is not impossible, just requires some trickery...

Q: 4. Does the Mini support the rearview camera as well (assume I have 4:3 screen).

A: If you have TV fitted, adding reverse cam is dead easy. Plug in to the TV's reverse cam input. Without TV you need extra modules. Both are available from BMW as factory kits. Or DIY it.

Q: 5. Does anyone have a link to the official part/pricing?

A: www.realoem.com

Q: 6. Can I get any MKIV to replace my current MKIII or are there differences I should be on the lookout for if I get a second hand?

A: Any Mk4 will work. If the Mk4 came from an E46 with RadioNav, then it will need recoding to Colour mode. Use my NavCoder (www.siegenthaler.co.nz/NavCoder/)

Q: 7. What are the differences between High and Professional?

A: High = nav map for use in Mk4, Mk3 etc. Professional is next generation nav system, different maps.

Q: 8. Anything else I should know?

A: Don't hesitate upgrading to Mk4, it's easy and quick.