Hi Scott

Magnetic effects have been factored into a number of models for the early stages, mainly to explain how the central star transferred momentum to the disk to become a slow rotator. Some scenarios for making chondrules [little melted blobs in some meteorites] involve an intense magnetic field around the early Sun causing induction heating or lightning-like bursts.

For accretion and/or core collapse models magnetic effects aren't really relevant, but for making the odd isotopic signatures in certain meteorites some sort of plasma blasting is indicated, and the transfer of momentum problem of any current nebula theory is probably only explained by magnetic braking.

Adam