I have had Bosch Euros on two different 300E's. Based on my 5 years of experience with this setup running typically 100/80's or sometimes 130/100's the vacuum height adjustment is very useful.

If you carry a load in your trunk the light you are going to get flashed. You can also move the light pattern up depending on the road circumstances.

The vacuum parts are cheap and by far the easiest part of the installation.
Someone made a comment about this feature being unrealiable. Not so in my experience. Works perfectly, with this caveat.

If you install relays and heavier guage wiring (recommended), then be careful with the gauge and the routing inside the housing. It can interfere with the pivoting of the light up and down.

Steve