I really got into the budgeting thing, allocating all my bills into categories. I stopped using it because I found I couldn’t split the bills between categories etc. So with that in mind I have 2 suggestions that would really enhance the service in my opinion:
Allow the user to split a single bill between budget categories. For example, if I spend £50 in Sainsbury’s £30 might be groceries and £20 could be household (new kettle / toaster etc).
Allow the user to create custom budget categories. For example I’d like one for lunch money, separate to groceries.