I have mine through ING locked in at 4.5%, got it 2 years ago this month. I've been extremely happy with them so far. At the time, every major bank wouldn't go below 4.9%, even if I told them I already at 4.5% somewhere else. ING also allows a 25% payment directly towards the principle once a year, when everyone else had 10-15%.
I also like thed fact I could call outside business hours, every other bank I had to phone before 5 (while I was at work) if I wanted to speak to someone in the mortgage's department. With ING I could call before 8, so I could go home have dinner and then call.
So that's the end of my advertisement