What do you think of the site search?

I'm looking for feedback specifically relating to the site search, at the moment I currently use Google to power the search this has its advantages and disadvantages.

When we launched I provided my own dedicated search system, but this sometimes didn't work for everyone, especially the autocomplete functionality. However I am quite tempted to write the system again.

Are you happy using Google powered search or should I write a new search system?

Good

• Google does all the heavy lifting and crawls the site itself
• Google generates preview text and thumbnails automatically
• Search works for all

Bad

• Google seems to add adverts to search results
• Google returns a lot of results
• Google lists results that aren't entirely relevant, for example showing a comments page with almost the same ranking as a main page.
• Search results aren't categorised