Like you guys said, I think W&H were great villains. They fit in perfectly in the Angelverse. I don't think the 'constant lawyer villain' thng would have ever worked in Sunnydale, but it fit fantastically in Angel's world.
Because while you technically did get different big bads every year (whether from Wolfram and Hart or other sources)you had this one constant- and you never knew whether it was a time they were trying to corrupt or kill Angel or if it was one of those rare times where they needed his help.
Plus, I thought Lilah was just one of the best villains ever. I love it when you see a shred of humanity and/or goodness in a villain as it just...erm, intrigues me, I guess, and you totally got that with Lilah. Especially when she started screwing Wesley (Screwing is the apt word here, no? hehe)