I really like YNAB, and I'm sad they've moved to this subscription model. If you buy classic, please be aware that at some point in the future it will become abandonware, unless the company changes their plans. I have researched alternatives that give me the control the YNAB does, and I'm kinda striking out.
I was never a budgeter before YNAB- I did a lot of look back analysis, and I saved a lot of my income (near half), but like others have said, YNAB gives me better control of my money. The forward looking nature of the app has given me the info I need to modify spending when called for so I can reach goals It also gives me the info I need so I can splurge. I love it. I also agree that the use of sinking funds has helped a lot. I was already doing this to a limited extent, but YNAB kicked it up a notch for me. I used to keep my checking balance quite low, throw everything else in savings, and then transfer back to checking when there was an intermittent bill (or vacation, or whatever.) And I'd do these cash balance projections- okay, plane tickets for vacation are on the next CC bill, that's due on such and such date, payday is next Friday, and these other regular bills are coming out... so I have to transfer over an extra $300 for the tickets. I have not done a cash balance projection to cover a bill since starting YNAB.
While I agree at it's core it's an envelope system, there's more to it than that. Because it's basis is double entry bookkeeping, it provides another level of assurance in that you cannot budget outside of the confines of the account balances. This sounds stupid, but it's a basic thing that a lot of budgeting tools I've seen miss.
As an accountant, I love it.
I don't want to, but I may shell out the dough for the annual subscription if push comes to shove. When it goes unsupported and stops working, and I can't find an alternative...