New to YNAB (started Jan 2011), so please forgive me if this has been address already, but this is the one major lacking feature of the application!
In every other way YNAB is awesome. I have already begun to evangelize it to others...but alas we really NEED this feature.
We already have our buffer and, as of last month, have zero retail debt. Some sort of "Goal" tracking functionality is what is sorely needed. I'm finding myself trying to figure out ways to work around this glaring issue by using a spreadsheet, but this adds unnecessary redundancy and extra work keeping it updated. It's definitely not an elegant solution.
I have a master category titled "Projects/Planning" and a sub-item category underneath titled "New Car - Wife". We have determined once that category balance reaches a certain amount (25% of the total price of the new car), we will begin car shopping. I really like PoundSterling's suggested approach. It would be great to be able to not only track the percentage "to goal", but to also be able to input a goal date and total amount of vehicle cost. These variables affect each other. For instance: Let's say we want to be at 25% by June 2011, we estimate the car will cost $35,000. YNAB would show how much would need to be budgeted each month to reach that goal by that date. Come May 2011, we get some actual "out the door" figures (upgrades, taxes, licensing, etc) and the total amount becomes $41,300. It would be nice to go into YNAB, adjust the total amount with the new figure, and then see how much more percentage wise needs to be budgeted.
This would also open up the door to some really nice reports. The ability to see how close you are to goals, or the completion of them, would be a huge psychological boost.
Perhaps Jesse can chime in on this?