The new KWSN clients are available here:

http://www.zadra.org/seti_enhanced/index.php?module=Downloads

Simon is working on a Mac client and he's talking about a Free-BSD client also.

I have the Pentium SSE2 client and it works fine. The speed seems to be about x2.

You can take a peek on my results and times here:

http://setiathome.berkeley.edu/results.php?userid=7831186

There are still no match for the Crunch3r applications The best KWSN client finishes the test WU for 67 secs and the Crunch3r - in 32 secs

Same here, Son Goku
Speed is about double that of the standard app. I'm using the SSE3 set.
I've only been using it for 8 days, but the difference is very good.
I never used an optimised app until now, but I wonder how well I could have done had I been brave enough to try from the start!