I shot a wedding a few weeks ago where I was hired just for the ceremony and to cover the photo shoot. The bride asked if I would mind following them to the reception to shoot them arriving. It was only 2 blocks from my place so I said 'no problem'. I decided to go inside with my HV30 to pick up a just a little footage. The lighting was absolutely brutal. Not just low light, but the light that they had, had been gelled with some purplish decals. The photog was severely distressed. I figured WTH, and went back to the car and took the 5D2 in, just to try it out. I was able to dial in the WB to around 3700k, and crank the ISO up using a 50mm f1.4.
Here's a comparison of the two cams. I know it wasn't a fair fight.
5Dmk2 vs HV30 low light test on Vimeo