I love the heads up display! So much so that I had to have the car ordered (and endure the long wait) because they couldn't find one with heads up in the color combination and with the options I wanted. Whether it is a must have really depends on the individual.

The reasons why I deemed this a have feature:
(1) I know if I don't get it, I'll end up wishing I had.
(2) Really distinguishes the car from other brands. I don't think anyone else besides BMW current offers this. At least I didn't see it in Mercedes and Lexus.
(3) If you are getting navigation, then heads-up really compliments it well. No need to take your eyes off the road
(4) An X5 already cost so much, whats the extra $1200 for something that can be used everytime you drive? Just like Comfort Access (yes. we can all insert the key and then start the car, but it's really nice not having to look for the key).