Played for the first time solo last night and I loved it. Once we all got up to a reasonable level it was good to see the diferences in the class set up really come through. You'll need a diverse team to make it through and some better tactics than we did but on the whole, very enjoyable. This coming from somebody who wasn't the biggest fan of zombies (read: I suck).
Riot shield now unlocked for it, so i'll be tanking it up next game and getting me some fire melee damage as well!! Bring on the aliens!