At the moment any category can be flagged an typically an “income” or “expense” category. This distinction is used to group the categories, and in fact reverse the count on the category.
For Income categories, the “budget” is a target you hope to reach.
For Expense categories, the “budget” is the maximum you should spend.
Probably we’ll keep tis distinction. We’ve discussed having sub-categories in the past with roll-up totals. We’ll probably do that eventually, but not any time soon, simply because there are other higher priority features.
Regarding transfers – having a single set of categories across all of your accounts nicely facilitates the target account entry. I’m liking the single instance of categories more and more. Perhaps, I’ll do that now in combination with transfers (before releasing transfers) since it will make things much simpler. Unfortunately the next system upgrade will be pushed until next week, but its for the best I think. I’ve discussed this with the other half of the design team and I’m going to go ahead with making categories a single global entity.
Also, funny enough… the current entry dialog DOES have an account field allowing you to create/move entries to other accounts. However, I have *just* removed it as part of the transfer feature. The account field is just clutter on the entry dialog, it never gets used. Behaviorally, people won’t create a transaction unless they are “in” that account and thus seeing the surrounding context. I originally thought it was a good idea as mentioned by Obelix, however, noone is using it, including me – its just another field to have to tab through.