The only way I would fund GIMP is if that funding went directly towards a better UI. It's not worth improving the algorithms given how hard it is to use.
I happen to like the UI. It's not for everyone, admittedly, esp. people coming from PS, but it can modified and rearranged. ATM, my Gimp UI is a single window will all the tools nicely arranged on the left side and only containing the most-used tabs. There are only 6 or 7 tabs you'll use 99% of the time anyways.
Same. I am no graphic wizard, i dont want to relearn. I am happy it still looks more or less than i when i learned it years ago, and pretty much similar to the last PS version i've used.
What's so bad about the UI? People often complain about the confusing multi-window mode, bug gimp actually have a single window mode for a while now, which make the layout looks somewhat like photoshop's.