Bing is shite, needs no recommendation, it should be destroyed. I'm not a Google fanboy, it is just bing really is bad.
The thing the current site search is missing is to be able to change it from 'everywhere' to something actually useful, and to be able to group results by post/thread rather than having every single tedious reply if you don't want to. Makes it quicker to find things in results, especially if the term you have searched for is in a thread title with hundreds of responses, you just get those 100 responses in the results along with the others.
Not saying it doesn't find anything, it just displays it badly and options to make it better aren't there.
It's the kind of thing that I'd make better in my job if this were my site as I do on my companies site.