I am a fairly new Warhammer player but here are my thoughts after reading the book for a few days.1) As a Skaven player, I have always had problems With both the armies of Chaos. With Storm of Magic, I can use some of the Daemon troops that cause me grief. You can also use units from Vampire Counts and Tomb Kings! There are of course rules to follow but the unit choice is pretty good.2) The magic is epic and many of the spells allow you to target a single unit, and in some cases obliterate it.
Existing magic spells can be made stronger by the Storm...this means the Dreaded 13th Spell can made even more able to turn opposing armies into rats.3) Every army in the game now has access to many of the creatures from other army lists, and lucky for us dirty rats, the Hell Pit Abomination is not among the them! It looks as if only creatures that appear in nature, the Warhammer nature, can be used. Some new models are also available. The dollar cost of most of the creatures are quite reasonable.4) If you don't want to spend money on new models right away, the book includes a variety of very powerful magic items. For example, you can equip your lords and heroes with a sword that, under the right circumstances not only doubles his attack characteristics, but hits and wounds automatically with each wound doing 2d6 damage!5) The fulcrums are an interesting addition to the game and due to their power, I can see even the most skilled tacticians recklessly sacrificing a unit or two to either hold or take them.6) Storm of Magic only contains two scenarios. Both seem like they would make for an interesting night of gaming but I think more would have been nice. Hopefully, White Dwarf will fill the void and feature some in the coming months.Overall, I think it is an excellent addition to the Warhammer universe. I don't think it is something that will replace your existing game but will change the pace from time to time. Storm of Magic games will usually be upwards of 2000 points because your allowance for the new rules will be a 25% bonus in addition to your army list. I think 3000 points would be the perfect point total giving you an additional 750 to spend on the Storm of Magic stuff.