I can't stand odors, probably comes from an alergenic, asthmatic, youth.
No little pine trees for me. Florida has to be about as bad as it gets for mildew growth on evaporators and in the last two years I have had it on both my wifes ML and my 540i. Luckily I hired a tech from Toyota about two years ago and he turned me on to the best stuff. It is hooked to the drain under the car and a whole aerosole can is exhausted. It creats a foam that permeats the entire evaporator case. After about 20 minutes it condenses back to a liquid that flows back out the drains. The kit also comes with a spray to put into the air intake but it smells so I didn't use it.
After first doing it to my wifes ML, I was really worried because the car smelled of amonia when I drove it home. I forgot about it for a week and then asked her if it still smelled of amonia. She said she never smelled it. I have driven the car numerous times since and absolutely no smells other than the new car smell.
We have used it in the shop a number of times now and I have one word of warning. Most older MBs have A/C drain tubes that are made of a foam rubber tube with 7/16 in wall thickness covered with a thin water tight film. The foam often is in terrible shape. The method of introduction of the product requires a tight seal to the bottom of the evaporator case. On 300Es that we have done we have had to replace the drain tubes after pulling the wimpy ones and hooking the product right to the evap hard tubes (inside the car).
Bosch Master, ASE Master, L1
33 years MB technician