This is one of the stronger Xander episodes of the first season. His reaction to that freaky clown is spot on, and it is a scary and funny moment at the sametime. Also love his continured scasham at the expense of Cordy.
The scene with Buffy's father is truly sad.
Overall, it has a nice idea at the heart of it, some good dark/strange moments, and some fine performances. But, at times the pace does drag, and not all of the stories come together as well as others.
Its funny how your feelings can change over time, because now I think this is one of the weaker season one episodes!
One problem I have is that the emotional pain Buffy suffers when confronting her father feels out of synch with the more comical tone of some of the other Nightmares represented in the episode. I just find the storytelling very messy in this one.