£600 including installation is a lot, they are not that hard to install.
There are two OEM kits, the difference is in the last bit of the part number:
729x supports most phones that support the BT handsfree profile. In theory the later the revision the better the support (although a 729C seems to be newer than a 729D - so 729C and 729E are the most recent versions)
730x supports phones with remote SIM access profile support only (see my post in the For Sale section for some more info on this)
They are both equally easy to install, pretty much plug and play - no cutting or splicing of wires needed although some dash and trim disassembly is needed and you will need access to someone who can code the unit for you.
If you have the red Highline MFD then you need the 729B unit (or a 730A or 730B if your phone supports RSAP). There are versions of the 729 unit up to 729E but these do not interface with the red MFD (the kit still works but you will need an RNS510 head unit to use it)
I have had an iPhone 3GS, an HTC Desire, an HTC HD2 and an HTC HD Mini all successfully paired and working (making/receiving calls) with a 729B unit. The B units are getting rarer but are still available - I bought mine two weeks ago.
A mate of mine has a Fiscon installed and the functionality is great, but he tanks it up and down the motorway every day and has commented on some people not being able to hear him properly when he's, er, keeping up with the flow of traffic.
If you don't have the MFD then I'd probably go for a Parrot kit with it's own display. These will work with any HU and don't need to be coded, although installation is a bit trickier because you need to place the display unit.
I should get out more......