The reasons why Skaven are excellent.
i) They are the bond villians of the warhammer race, complete with underground lairs and WMD's.
ii) The Skaven though lacking mass archers have flame throwers (anti-regeneration) and Ratling guns, those ponsey elves hate them
iii) Doomwheels
iv) The life is cheap rule for the poisened wind globadiers is so much fun when you lob twenty into a melee. So you'll kill 10 rats, they are so much cheaper than the chaos warriors who discover they have no armour save 8).
Admittedly they have their flaws but under the latest rules at least they can hit a barn door, more than they could when I first started playing!