I'm going to lay it all down right here. I've been wanting to do this ever since relaunch but I wasn't sure if posting individual problems would even get them read.
The GOGmix character count includes hidden characters, so you can have a 250 visible character count and still be over if you use, say, quotation marks. It should count visible characters instead. GOGmixes should have a save draft feature, at least a single slot, so problems like this can still be saved without you having to lose EVERYTHING because you can't save entries with more than 250 characters.
When editing a post, carriage returns are eliminated for some reason, meaning you have to go back and add them all again before reposting.
More interconnectivity between pages would be nice, so that you could enter the various pages of your profile and have a one-stop area where all the information can at least be accessed. Sometimes I need to click multiple times every time I drop by to see everything.
The game shelf now loses organization when you move away from it. It keeps the order, but if you have things placed on the shelf with spaces in between, the spaces are lost.
Would be nice if there was a profile page where you can make some general statement about yourself, but I don't know if this would be abused.
In the game descriptions, I often don't get a feel for why the game on GOG is improved. We own Baldur's Gate already, but when I look at the BG game page, I don't get an impression of why someone who owns a hard copy would want to get BG here. Maybe there isn't a reason, but, say, you could talk about disc swapping being a thing of the past there, you could talk about famous errors that are corrected, that sort of thing. Be proud of the coders' work on the games and show it off a bit. That will get more buyers anyway, I think.
Symbols are sometimes not defined on certain pages they're used; they need a general popup for definitions so people can all be on the same page. The color-coding dots and other things aren't memorable for me (in my case, I think more in shades of color than actual colors, if you know what I mean).
When looking at the "my posts" and "my questions" pages, there are boxes underneath the heart column that, when you click on them, it merely causes a reload and does nothing. Are these supposed to be checkboxes?
In forums it would be nice if you could reply to multiple people in a single post, rather than having to make multiple posts.
That's all that I can remember right now. Let me know, GOG staff, if that was helpful at all.