HUD is the greatest thing ever....
I borrowed a 6 series convertible last year and hated the reflection of the HUD box on the dash that you see in the windscreen as a square.....if id ordered a new 6 I woudnt have oredered it and that would have been a huge mistake.
However I bought an bmw M6 instead so was stuck with it.....
I found you need more than a day with it to get used to it...after that you dont see the reflection of the dash piece anymore and just the figures....
I coudnt live without it now, not just for those moments when you suddenly see a police car (its by far the quickest way to see how fast your going) but for general use, it makes it easier to keep within speed limits as your current speed is always in line of site....
Also makes navigation easier as you dont have to look at the map/screen for directions.....
Would be really nice if it did bluetooth numbers as well so you see whos calling! Sadly it doesnt.....
Dont know if the m'sport e70 will have the M6 style HUD with rev counter that would be nice!

Put simply an option you cant live without if you use it correctly.....
My new e70 arriving next week doesnt have it, but the e70 msport arriving in jan 08 will.

Will miss it a lot by then!