I love my HUD and ordered mine blind based upon what the brochure said. At £800 I thought it was a bit of a pricey option for what I just thought would be the speed being displayed but it is so much more.
I thought I wouldn't be using my nav more than a couple of times a week but I use it every day I go out to where I'm going and every time when I'm coming home. The route has been known to change based upon carnage on the motorway and the nav has guided me round it.
I love my HUD and at £800 I think it still remains one of the better options to add. It does integrate with the nav and will display which lane to be in, which roundabout exit to take and the countdown to the junction etc.
This is definitely one option I will be adding for my next car too