With both the kit lens and a prime lens.
Sony NEX-EA50 Low Light Shots (http://player.vimeo.com/video/56769496)

Another shot of the waterfall ice sculptures with the NEX EA50 - one second exposure, 50mm

I've shot pretty extensively in low light using old fast primes. Go to Robert Moran on Vimeo (http://www.vimeo.com/remoran) to see the short caroling video done with the 20 and 50. Low light to the max rules but all in all, both systems did pretty well. What some folks don't know is the fact the on board mikes for both cameras are amazing, something pretty evident in the short piece as the 20 did the heavy lifting in capturing the singing 500+ people did for a good cause. :)

Since I just got my adapter to fit my Samyang primes I did some quick comparison in house (sorry, no video to post) and compared my 550d and the ea50 with a 14mm f2.8, 35mm and 85mm f1.4.

If I used the neutral preset on the 550d the ea50 had a better low light performance and only once I applied the technicolor cinestyle preset the 550d got the upper hand again. For those that have used the very flat cinestyle preset know it make quite a big difference to any factory presets the 550d has. But since I need to bring back the colours and contrast in Edius they end up being the same. So end conclusion? The EA50 gives me the same low light performance as my 550d but only if I apply the cinestyle preset with a lut curve to the 550d footage, at the same time the ea50 is visible sharper which makes the image just look better, with the 550d fine details turn to mush at high gains while the ea50 retains more detail. I did use the factory standard PP3 preset which is the flattest avaliable but still retains enough colour and contrast to use as a base for further colourenhancement.

Regarding noise they where pretty close with the EA50 appearing just a little bit noisier at 1600, 3200 and 6400 iso. I would not use this camera above 1600 iso, 3200 is usable after applying neatvideo and 6400 just looks plain ugly. The footage from the EA50 would withstand a neatvideo treatment better then the 550d just because the footage is much sharper, with the 550d small detail at high gains turn into mush which is not the case with the ea50.

Low light wise I"m satisfied but had hoped for less grain, still compared to many small(er) sensor camera's it will perform very good with fast primes, just don't cranck up the gain too high.