This camera improves on an already good camera, the Sony EX1. It adds SD recording, a better viewfinder, cache recording and some improvements to some button placing.
It's still possible to us SD cards in adaptors to record HD instead of buying expensive SxS memory cards but that does mean that you can't really shoot slo-mo and that if you are copying off the cards onto hard drives your data rate will be lower on SD than SxS. Class 10 SD cards are recommended you can use class 6 but I've had problems with some of the Transcend cards.
This camera is pretty good in low light, certainly better that the Canon XF305 but that's not too surprising as it has 3 x 1/2" sensors rather than the Canon's 3 x 1/3". However the Canon has a better lens, in terms of quality and reach. Accurate focusing is key and this camera has all the professional tools to help, peaking, expanded focus and a great screen and viewfinder.
Like the XF305 this is not a light camera, people moving up from previous generations of pro-sumer DV cameras will find it heavy, and as a result this camera requires a decent tripod to get the best results, something like the Miller DS10.