It actually looks really neat. And it doesn't have too many undead in it, so you don't have the problem of 'Clerics do too much', at least compared to what you get in other campaigns, where the final bosses tend to be undead.
I amused myself one evening by designing a character that would be able to command every single undead in the Castle Perilous. There are 2 vampires, an Advanced Brain in the Jar, and a rather advanced Lich, if I remember correctly.
So, that's the end of my griping against Undead enemies. Unless the DM throws on Quells.