Ha! I assure you, I have endless joy driving with the windows down, tunnels and built up streets are particularly entertaining!
I received the complimentary BMW Pro upgrade and cannot tell the difference from my old base spec E82 system - it's the only thing I'm disappointed with. Good choice going for the HK.
Couple of other recommendations,
Heated seats, great for driving with the windows down...
Vis pack - very impressed with the dynamic high beam.
Front parking sensors - although only necessary if you live in a city or have a tight drive.
The privacy glass also looks good.
Hope this helps.