There are quite a few new features included in 4.3: personal hotspot is indeed included on the iPhone, although it needs to be enabled on the carrier side to work, and the iPad's side switch can now be set back to being an orientation lock, which should make a lot of people very happy.
ENGADGET: iOS 4.3 beta arrives for devs, brings AirPlay video support to apps, personal hotspot and customizable iPad side switch (update: video!)