This is just my opinion here, not the gawd given truth, but hey I use the site a lot to upload stuff and get picky about GUI's, so I I believe it has a lil weight.
1. Get rid of the keyword suggestion popup thing!!!! I can type "male" in 2 seconds flat, the suggestion popup waits till i'm done and already typing on the next keyword box to show me a suggestion for the first!!! So I have to wait for it to disappear to be able to even type anything. I'm very certain that people who can read text can also spell correctly and type it into a box, especially small keywords.
4. If I look through a comic and want to get back to a person's gallery, I instinctively hit the back button, but this only goes back to the "last page" you were on, which is the same submission. Yes there's a "gallery" button, but can you find it quickly through all the other stuff on the page? It doesn't take you back to the gallery page you were on either!!! So it's not very useful. I have a lot of submissions...I know!!
5. Lots of wasted space in the visual design and clutter. Am I the only person that finds the interface a bit much? Text isn't really the best way to "talk" about this one, I'd rather slap an image here instead. I've heard of a few people refusing to use IB simply because it was hard to navigate for them. Don't get me wrong here, I like the site itself, lots of good stuff here, but argh...it could be better!
6. More API stuff pleeeez. I was making an app to work around the "pool" system's way of arranging images, but then I found out there's no support for edit pools...doh! So I stopped working on it. Using curl to get tokens and all the secure junk is a lil over my head ^////^ *sigh* I'd love to have a drag and drop app....
7. Replies. So I want to reply to a long comment, *clicks button and watches the page scroll all the way to the bottom and place a tiny snippet of the full comment above the comment box*. Uh, it'd be super wonderful if I had a visual memory that could pick words off of a page of text, but my brain doesn't do that. I gotta see what the heck I'm replying to!! My usual work around for this is: *use launchy to quickly open notepad, middle click it's "X" button to stick it "always on top", put it over my browser, and scroll through the long comment, copying bits to quote and replying to stuff, then copy all that I typed, pasting the comment box...yadda yadda. Surely it's possible to have the full comment in a neat little box that scrolls? Or maybe a seperate page with half it's vertical length being that comment, and the other your reply for easy editing?
8. Adding submissions to pools could be made into a small drop down menu or a box that scrolls, does it really need it's own page? Also, there could be a small dropdown menu on the page of that submission (after it's been made public and all that jazz) to pick a pool, and an "add" button beside it that does the job. This would only show up for the owner of that submission o'course. The dropdown box could also be a combo box, something you can type into as well as select from. Images aren't always necessary for menus, and would totally avoid the need for a whole extra page.
9. Horizontal space could be used more. I notice some long descriptions under some options that have really small titles. Like "character sheet" in the "Edit Submission" page. Couldn't these long descriptions just be tooltips. What about using the "title" attribute? http://www.w3schools.com/tags/att_standard_title.asp This way, you could stick those check boxes next to eachother. Same deal with the rating section. You could add plenty of stuff to read without gobbling up all that precious space. The descriptions don't always need to be there in the user's face. After a while, you learn what everything is for and it's easy, no need for reading.
That's about all I can think up atm. Yes it's little stuff perhaps, but repeat that little stuff LOTS of times over a day, a week, a month....it gets old!! I don't really browse the site that much, but even just being an uploader, it irks me. /rant