The Warhammer Alliance has posted a nice little review on the Magus. Although a quick read, it covers a decent amount of issues that players have. This review offers not only a fairly objective look at the class, but also a nice discussion on the review and class as a whole. Definately worth the read, so check out the full review and join in on the discussion!
Lore & Tactics
"Those selected by the Dark Gods to receive the ability to cast spells are held in high esteem by the tribesmen of the north, for they have been singled out and granted vast and terrible powers. All manner of Daemons are counted amongst the numbers of the Raven Host, but the Magus uses the power of only one such creature: the arcane and powerful Disc of Tzeentch. He is forever bound to this living platform, and it is utterly ruled by his will. Channeling his dark energies through his Disc, mortal and Daemon achieve potent synergy, leaving only devastation in their wake."