<p>While I know IronRuby isn't quite ready for the world to use it, I was wondering if anyone here tried it and tested how well it faired against the other Rubies out there in terms of raw performance?</p>

<p>If so, what are the results, and how did you go about measuring the performance (which benchmarks etc)?</p>

<p><strong>Edit</strong>: The IronRuby team maintains a site on how they compare to Ruby MRI 1.8 at <a href="http://ironruby.info/" rel="nofollow noreferrer">http://ironruby.info/</a>. Below the spec pass rate table, they also have some information on how IronRuby performs on these specs. This table is not continuously updated, but I assume they update it often enough (you can see the last update at the top of the page).</p>

I have used it and it has worked great for what I have done.  However my measuring of performance isn't really scientific, because it was all visual.  However I did notice that IronRuby seemed a little more snappier when I compared the two program on equal tasks.  I really think this had to do more with the strong and tight binding with IIS that .NET has more than the speed of the framework.
But I could totally be wrong, because I didn't really stress my applications to the levels that Twitter might see.  But from my .NET experience I know it would hold up just as well if not better than current production Ruby applications.
By the way I tested Ruby using FastCGI under IIS.