Nutritional scales are different than regular scales - they do more than just weigh food, they actually provide information (based on the weight) such as the calories, fat and carbs of the item being weighed. I just wanted to mention that, as the above posts are geared more to regular scales, not nutritional scales.
My child has Type 1 diabetes, and as a result of this, we need to know the exact carb count for everything he eats. We bought the Salter Nutritional Scale, model 1450 - this was based on a recommendation from the dietician on his diabetes care team.
http://www.rightonscales.com/web/1450.htm
The scale is amazing - I wouldn't trade it for the world!!!! We opted for the 1450 over the 1400 as we liked the look of it better, and because we liked the built in food database (over 1400 foods, compared to 900) of the 1450 over the manual-entry database (you have to look up a food code and enter it) of the 1400. It works incredibly well, and is something we all use every day now. It's helped us so much - for instance, if my son wants a banana, instead of guessing the carbs based on a calorie/carb book (the banana in front of me never seems to match the size of the one in the book!), I can weigh the actual banana he's going to eat and find out the exact carb count for THAT banana.
I'm calorie counting, and the scale is worth it's weight in gold for that reason, too. It's wonderful to be able to weigh a chicken breast, for example, and know not only the weight but the actual calories for that piece of chicken (I hate guesstimating based on a calorie-counting book!). You also get other information, such as fat, saturated fat, fibre, GI rating, etc.
Other features of the 1450 are the ability to add your own custom foods to the database, and a handy "quick list" of the foods you weigh the most. I'd highly recommend it, and it's more than worth the money....can't say enough good things about it!