I'm pretty new to the forums, but I know a lil something from what I learned from here.
The stage 1 performance tune is very basic and is really only a small boost increase of 3-4lbs. Very safe and warrantied by BMW anyways. You should also not worry about cooling because the stock FMIC is just fine up to about 400hp when I see guys start to upgrade to stage II and such.
IMHO, I would rather spend my money on a flash tune. You'll easily put down 3x the power and it'll be a lot more fun!!
These engines are pretty tough so I wouldn't be too concerned.
It also depends on what you're looking for. If youre worried about warranty I'd stick to a COBB as you can flash back to stock. (it's plug and play) and dealer will never know you had it.
If you have more specific questions I could possibly answer you more clearly. Goodluck