1) IMO The M3 with a supercharger is a super car ! It puts a smile on your face every time you drive it ( i call it therapy
2) It's a big difference from stock it's a totally different car
3) i have never experienced any issues with my kit.
4) I personally would recommend getting a inter cooled kit ( power is more efficient & keeps temps down )
5) The difference in the ESS staged kits are Software, injectors , intercooler & pulley/boost .
6) I get my oil changes and services as i would with out the blower with out any problems ( I've went to 4 different dealer's with out any problems whatsoever )
7) They won't void your warranty just because they see a blower now if you came across a problem due to the blower that's a different story .......
8) Choose the Kit/company that best suits your needs "" Peaceful""
9) BBK is not really needed if your a spirited driver , now if you have a heavy foot then yeah get BBK ( although it's smart if you equally upgrade all levels on the car Power/Brakes/Suspension )
10) you said it yourself their is not one unhappy ESS SC'r owner ( problem free and that's with 150+ kits sold )
Good Luck on your Purchase