We have just gone over 240,000 posts, and we have been using it for a while now. It provides better search results, as it has stemming analyser for various languages, so you can get different versions of the words being searched for as well.
XFES requires that you have elasticsearch 0.16.0 or newer installed. As such, this add-on is only applicable if you have root access to your server (such as with a dedicated server or VPS). XFES also requires XenForo 1.1.1 or newer.
That's too bad, would have loved to use it! With that being said, not sure what VB uses but I never had a complaint from a member about a search and I generally find what I am looking for flawlessly! i hope Xenforo's bare bones search feature is at least as good as VB3 has on my site. thoughts?
Any limitations in the default search are due to MySQL search though.
Here's some relevant information from the FAQ:
Why can't I search for words with 3 characters or less?
This is a limitation of the MySQL Full Text search function. Find more information on the MySQL site.
Note that with XenForo 1.1 and above, it is now possible to set the minimum word length in the ACP -> Options -> Search Options: Search Minimum Word Length; this value must correspond with the MySQL full text minimum word length in the my.cnf configuration file.
Why can't I search for certain words?
The MySQL search function has what are called stopwords, which are typically common words, and are excluded from searches. Find more information on the MySQL site.
Note that the XenForo Enhanced Search add-on, which is installed here on XenForo.com, does not suffer the same constraints as default MySQL search does with regards to minimum word length and stop words. The stopwords for elasticsearch are listed here.
How do I search using OR instead of AND?
Use "|" between words, for example: xenforo | software
@Brogan, do you know what template off the top of your head that would be edited so that this information could be relayed on the search box that pops up when you click in the search field. It would probably help the end user if an example (as you did) was given there.
I've also noticed that certain punctuation is sometimes an issue. If, for example, you search titles for keywords separated by more than one hyphen it will return zero results. There's been a couple more I can't remember off the top of my head. I'm mostly happy with the default Xenforo search, though, I've certainly encountered worse.