If I've understood it correct, the issue is if your Omega doesnt have the HIDs from new, then you've got 'manually electrically' adjustable headlamps (ie: for when you have full boot, obese relatives etc) this is bad enough if adjusted wrong when you're heading down the road with Halogens, however, once you stick Xenons in the mix, if you get the height/angle of beam wrong, then you're dazzling every oncoming driver (and the guy in front of you, of course, via his mirrors) The auto-leveling system is exactly what it says on the tin, automatically getting the level of the beam correct, nomatter the load on the suspension.

It's a legal requirement for any brand new vehicle with HIDs to have an autolevelling system, and therefore so, too should it be for retro-fitting.
Can't say why the Vectra boys don't seem to care about dazzling other road users, perhaps the wearing of baseball caps in conjunction with consumption of Stella whilst bathed in blue LEDs causes detrimental brain activity...
