I use Mint to stay aware of what I spend money on. I've always been obsessively frugal when buying stuff and Making puchasing decisions so I've yet to use it to control or limit my spending. It is nice for taxes at the end of the year as I tag things that I know can be written off, export as a csv, and give it to my accountant. He's much more liberal about writing things off.
I like how automatic it is and it captures all my accounts (PayPal, checking, savings, two CCs, and my investments).
It's also pretty good at categorizing automatically which means less work for you.
Random user and I have a Google sheet to make sure that rent and the bills get paid and so we can be more aware of our electricity (something we thought was rather high the first two months of living here). That's less about budgeting and more about keeping track and making sure one of us pays stuff.