I have the Tanita BF682, a $90 body fat scale that's accurate to the .1%.

In the 2 months I have been using it, I have found it to be very accurate, sometimes too accurate. I have found the best time to measure my body fat is when I wake up in the morning. The % may fluctuate, but over time the results are obvious.

My results looked like this:

Week 1 (Varied between 39% and 42%)
Week 2 (Varied between 37% and 40%)
Week 3 (Varied between 35% and 38%)
...
Week 8 (Varied between 28.0% and 28.9%)

It has seemed that the lower in weight I get, the more accurate the readings get. However, the net result was obvious. I used MS Excel to make a simple graph of it and though it jumped up and down, the general trend was plain.

Using the numbers, I graphed my body fat vs my lean weight and its nice to see that not only am I dropping weight, but my lean mass is increasing as well. That's pushed my goal weight up from 220 to 225.