I have them fitted to my BMW Motorcycle (the simpler H7 ones) and they don't seem to cause a problem (I don't get 'flashed'). Landrovers, etc. use reflector lights, most of the factory fitted HID's use projector lights which have a very accurate cut-off - my experience is that it is the projector lights which are the most 'blinding' if not aimed correctly.
I've no experience with the Land Rover, but the ones I've fitted H7 and H3 are pretty straight forward.
Oh - you need to be careful, the wire from the ballast to the burner (lamp) pulses at 23,000 V!