I've got a Disco transfer on my TD5 110 and when combined with the bigger intercooler, remap and all the other bits... Its rather nice
Drove them with standard gearing and a long journey is much more tedious with them. The reduced engine noise and extra fuel economy is well worth it.
Only minor drawback is 1st is abit tall when pulling off while towing heavy loads so probably would save up for an over-drive instead of the disco box if I didn't have as much torque.
In saying that, I also have 33x12.5s under it lol