Changing over to synthetic is fine as long as your car doesn't have very high miles(150K+). An engine can get acustomed to a certain oil, and it is usually better to stick with it. THat being said I recently changed to synthetic at 90K. Mobile1 is good (probably the favorite here) but I decided to go to Redline. Very good stuff from what I've read as well the opinions of a few mechanics I spoke with.
As for the other fluids, it just depends on how anal you want to be.
Technically, they say to change...
Brake fluid every 24 months
Transmission fluid every 12 months
Coolant flush and replacement every 12 months
This is merely a recomedation by BMW, it is probably safe to follow it loosely. Some may suggest intervals based on mileage, but I assume the aforementioned is based on typical driving (12-17K miles/year).