High tech scales: hype or helpful?

I weigh myself almost every day, but I don't live by those numbers. I know that they fluctuate (I usually get a fluctuation of about 2 or 3 pounds) so I try to take a long view on my weight loss. I do wish that I could more accurately monitor my progress - seeing the numbers change is really encouraging to me.

I measure, but I would like to more accurately monitor my body's composition. I know that calipers and hydrostatic weighing are accurate, but they aren't really an option for me. I was wondering if anyone has experience with those high-tech scales that purport to tell you your body fat percentage, resting metabolic rate, etc. For example: http://www.amazon.com/Omron-Full-Sensor-Composition-Monitor/dp/B0020MMCDE/ref=sr_1_1?ie=UTF8&qid=1296068108&sr=8-1. I just found that after a quick search on Amazon, but I know there are a ton of scales like that.

Do those scales actually work? They are expensive, and I'm not really all that confident in their claims, but I would love to hear anyone else's experience with them. If they do work I'd love some suggestions.

Thanks!