When I had my serious weight loss following Dr. McDougall's plan back in 2002-2003, I lost ten pounds per month for the first five months, then seven the sixth month. The last 13 took about two months for a total loss of 70 pounds.
My guess is that the speed of weight loss depends on how much one needs to lose and for me at least it did slow down after losing the first fifty.
Unfortunately, I slowly starting adding back in oils. Not really on purpose, as I wasn't adding oil to my cooking, but I started eating out a lot more, where it was harder to control oil in my food, and started eating nuts and avocado again. (I was going through an extremely stressful time and was away from home a lot due to taking care of a terminally ill loved one.) Fifty of the 70 pounds I lost stayed off, but I slowly gained twenty back. In the first ten weeks of 2010 I have lost 18 pounds. Not nearly as fast as the original weight loss, but I had a lot less to lose.
I want to lose more than the first 70 pounds I lost. That weight loss was wonderful but still left me at a size 12 or 14 jeans. And I want to be thinner again, as I have been almost all of my life. I don't believe I will be seeing ten pounds per month, but I am very happy with the 1 - 2 pounds per week loss I have been having.
Probably more than you wanted to know.