[mistwang]

OK. the request rate throttling bug has been fixed in current 4.0b1 package.
The litespeed is powered by 4.0b1 now, For the cache, you can try http://store.litespeedtech.com/, the page are cached for 5 minutes, the first access is slow, the subsequent access is instant.

cache is not a solution for everything, like vB cannot take advantage of it as the content is based on cookie (user login) and the response header does not allow caching.