DW and have been long-time Quicken users. The reasons why have changed over the years. When we were first starting out, budgeting and expense tracking was very important because money was tight. Our budgeting has become looser, with broader categories, as we got to know our spending habits. I also tend to use budgeting for forecasting and planning: buying a house, having kid, moving overseas. While Quicken's budget tool is pretty obtuse, it was handy to not only have a new budget target, but also the baseline of our then-current situation, to get a feel for what would be more and what would/needed to be less.
Now, Quicken comes in most handy for managing investments and around tax time. We will still have some investments homed internationally for a few years, so It's always good to have an overview, when you know not all your accounts will be sending 1099's. We are also tracking our sales tax spend, since TX doesn't have a state income tax. I don't think we will be regularly itemizing any more, but we have made big purchases in the last year as we settle in, and could add some money to a refund if we ever have a year with big medical expenses.