While the old Nissan subcompact never made it to the top of the IIHS rankings, the new sedan earned its award by scoring "good" ratings in front, side, rollover, and rear tests and coming equipped with standard stability control, according to the IIHS. The 2011 and earlier Versas only scored "acceptable" in side impact and roof strength tests.
Keep in mind that the Top Safety Pick only applies to the new sedan, as a redesigned version of the hatchback has not yet launched. The 2012 Versa hatchback is the same design that's been on sale since the 2007 model year.
See below for a video of the IIHS side impact test on the Versa sedan.