Terribly inaccurate, IMO.
We have a scale version as well. It consistently shows my BF as being 10% higher than on the hand-held electronic versions, which are consistently 5-7% higher than the good old-fashioned calipers. Which do I believe? I like the calipers because they are the lowest (currently at 18%)!!
Now, the scale might be a bit goofy because of my size (6'3", 250 lbs), but they are supposed to account for that. Also (not to sound gross), if you use the scale to test your BF, use the toliet, and test again, the BF number can change by a percent or two. I use the BF scale to only monitor long-term trends.