I recently got a promo copy of the new Skavan book for warhammer and after reading through it seemed they almost tried to change the nature of the army. First they made slaves cause panic in other slave units thus putting a hurt on the horde. They also made them blow up which is interestingly good against small armies. Then they turned on the SAD armies and really changed the shooting aspects of the army by making the Lighning Cannon follow the rules for cannons, Jezzails no longer skirmish, and ratling guns have to roll to hit. Further the engineers no longer get to cast a 2d6 s5 magic missile. With these two armies nuked there were other changes like the night runners no longer skirmish, the poison wind globidiers are now special, and clan rats no longer come with shields. For all these changes they did add quite a bit to the army. There are 3 new units, 4 new mounts, and 2 new weapon teams including one which does inpact hits. They returned both the vermin lord and the doom wheel and created a new warpstone mutation the Hell Pit abomination. The Assassin is now playable but is both more expensive and way worse than the dark elf one. Finally there ware many interesting tweaks to the magic items, spells, and units to make the army different than before. The sum of these changes seem to be the creation of a better fighting army with many diverse coices for shooting to help out the combat troops.
On the whole it is an interesting book. The army still retains the plethoria of special rules which makes reading the book tough. The book also seems to be alot weaker than Lizardmen, deamons, and Dark Elves which is not a bad thing but will make it scarce in tournaments. On whole those with armies will be very happy.