I'm not an active user myself (I've never had the need) but Numpy and Scipy are two of <b>the</b> key modules people cite as their reason not to use or port (or support) Python 3 (due to lack of porting). According to this announcement to Numpy-discuss, this will very quickly no longer be the case. Numpy has been ported to Python 3, and Scipy is following quickly (in progress). These are cornerstone libraries for the community - more will follow.
This is great news; most of all, I'm looking forward to picking through the collective knowledge of their porting effort to see if there information which can be given/provided to other porting efforts. You can see their Python3 porting notes here.
And a quick plug - the PSF Sprints project will help fund sprints focused on porting libraries to Python 3 - go here.