Motor On- is this a problem? is it gonna cause me future problems? or is it just going to be an annoyance i have to live with like so many other mini characteristics?

 

It's not so much a problem as it is an annoyance, I had mine swapped under warranty, the dealer played dumb to hearing it several times, then admitted it was there and normal and then I told them I went to a meet, other cars didn't have that sound so they replaced it, the knock went away.

Lightweight flywheels will make the same type of noise, and from what I'm told actually a fair bit louder. There's several people floating around the boards that can give you a much more technically sound description of exactly what in the design is causing the noise, I used to be able to but a few details like that have slipped the memory over the years after I stopped having the issue first hand.