However, because of everything I've read (and learned about PHP, the language) since the announcement I'm not particularly excited about HipHop.
me neither. a php-to-c++ compiler ... how boring!
also:
Almost every single website on the internet is I/O bound, not CPU bound, web applications spend their time waiting on external resources (databases, memcache, other HTTP resources, etc.). So the part of me that develops websites professionally isn't super interested, Facebook is in the exceptionally rare circumstance that they've optimized their I/O to the point that optimizing CPU gives worthwhile returns.