I like LoseIt. The food database is not crazy, but a lot of stuff in there anyway. The interface is straightforward, data is presented pretty obviously... it is actually easy to use.
Weightbot is neat, but gimmicky, graphs are crippled by gimmickery.. still, I paid for it and use it, as it's purty quick to enter daily weight and it does export, so you can analyze data in Excel. The Weightbot designers don't "get it" when it comes to graphs and what data people losing weight want from their data (for example, it doesn't give you an averaged-out/smoothed-out current weight number... you enter 3lbs extra one day, it tells you that you've given up 3lbs worth of loss progress... for another example, graphs are rigid over month boundaries.. so if you made some strides in the last week of a month and then the first week of another month, well, good luck getting both those weeks on the screen to analyze). They do "get" how to make data entry easy and slick-looking though.
I did not like Sparkpeople, as it didn't account for my exercise in a day. So if I went for a 750 calorie run, it would still tell me to eat 1700 calories for the day, which was already a 500 cal deficit over maintenance, adding up to a total of 1250 calorie deficit... too much for one day, IMO. Whereas LoseIt adjusts the budget up to 2450, so then I can go and eat more stuff and know I am still on track.