I've used Mint for some time now, and they are very reliable. They aren't terribly accurate in my experience, as I can pay a bill and then 2 weeks later when the due date comes up, Mint will still send me an email stating that the bill is due. They do offer some cool charting functions and visual representations of your savings and debts, and as a whole it is a neat way to keep track of all of those things in one place.
For me, there's just nothing easier or better than keeping my own books at home on paper. When I do it myself, I can organize and represent things any way I want to, and I just find it easier. Still, for someone who does not like keeping their own books, this is an interesting and free way to try software-based solutions.
Just as an FYI, I've also tried recent versions of Quicken, and I found it to be cumbersome and limiting and overall, not worth the money or time.