I left the cliffhanger in Week 1 struggling with the logo. After much revision, including the standard false "ah, this is it" moments at least twice, we got there. (Sorry it took so long team!)
I will unveil as soon as I am able (couple of weeks probably) but I think we struck a balance between obviousness and subtlety.
Nicely it lets us do some interesting customisation based on user activity, clearly inspired by the ace Dopplr http://blog.dopplr.com/2007/10/23/in-rainbows/ 'sparklogo' that changes with cities visited and building on work from /dev/fort4 performing colour frequency analysis on content the user sees. Look at pictures of blue skies and the logo will start reflecting that, dive into something else and primary colours might become prominent. Ah, you'll get it when you see it.