The keyboards that come with Macs look really nice, the quality seems pretty good, but I just cannot use a flat keyboard, after a few days my wrists and hands started complaining big time.
After some searching I came across the Kinesis Freestyle keyboard, they make one with Windows layout and another with Mac layout. They are not cheap, however I use a keyboard all day, every day so for me it is worth the money.
If you get the Freestyle you also need to get the Freestyle VIP - Keyboard accessories kit, otherwise you basically just have a flat keyboard again
The VIP accessory kit will give you 10 and 15 degree angles, they also have some other accessory kits that will give you up to 90 degree angle, I believe that kit is very expensive, the 15 degree works fine for me, but the Ascent kit looks interesting.
Eight inches of cable between each side of the keyboard, put them where you want
pivot point if you want them close and asymmetrical
10 degree
15 degree