The overview page shows proportion of budget used for each category up to 100%. After that its hard to tell at a glance how much a category is over budget (if its over). If for example I spent 50% more than budgeted for a category the bar indicator should be coloured 2/3 regular colour for the category and then 1/3 some other warning colour.

Either that or some indicator showing 50% over. I know the dollar values are there, but its not obvious at a quick glance.