I use it and while I like it more than the other options for entry and the number of items in the database, I wish it had more reports (like caloriecount.com). No reason not to, after all. The data's all there -- they just need to make it available to us.
I tried the 5-day free trial of the gold membership and didn't find anything about it that made it worth paying for. I thought the mobile access alone would be worth it (when I access the website on my droid, it doesn't work very well -- when I click on the food, it invariably chooses to click on the link "underneath" if that makes sense), but the mobile access is different and not very helpful.
I agree with fitkristi that the calorie burn is way overestimated, particularly for running, so I enter all my exercise manually. And as Ashley Nicole says, there can be inaccurate information -- when I can, I always choose the "verified" option, and double check that it makes the conversions correctly (like if I enter grams instead of servings).