Perhaps the deadliest sin committable on GOG...

Gifting a game to someone, only to find out it's a NES alt.

followed by Negative Rep!!!

Any gerund preceded by the word regional.

Then just scammers and trolls in general. :\

Not sure how deadly is this but,

Forum has no mobile version

Guess it's more of a youthful mistake than a deadly sin, but...

The whole "Movies" section.

In random order:

+ website - slow, doesn't scale on smaller screens (isn't "responsive")
+ forum - quoting, posting often fails, rep abuse, spam, search is bad, can't see posts by user, see above
+ browsing games - add more (sub)genres and other filtering options, but most importantly, allow combining them
+ browsing games - allow people to filter out DLCs, upgrades, deluxe editions, and in-dev games
+ chat - makes zero sense for a forum, but since the deed is done, recover the remaining PMs please
+ communication - if not for judas, would we ever see the blues on matters that have nothing to do with support tickets?
+ communication - "too niche" has become a tired meme in your own community, how about becoming more specific?
+ communication - could you stop trying to spin bad news in a negative manner? price hikes and regional locks aren't "Good News"
+ library - change the game counter when the number of displayed games changes (example: I click on "Linux", number of games stays the same)
+ library - only one tag visible per game...why?
+ reviews - missing reviews, vanishing reviews
+ rating system - most games on the site end up highly rated thanks to the 1-5 scale...numbers are Free, add more
+ the fine art of game acquisition - I won't suggest you add 600 indie games of mostly dubious quality, but damn, you have committed mistakes and omissions
+ getting tired - get me another coffee? some cookies too. I like chocolate chip. thanks :)

No, I want more movies. :'(

Good News™
Regional Pricing
Regional Locking
No more manual sorting for the library
No more movies

Why GOG removed custom/manual sorting feature? :-(
Any reasons?

Missing reviews
The umpteen nes alts
The regional locking for our Aussie and German bretheren
Regional pricing (though not as bad as other platforms)

The rest is good though. Support works well etc.

It would be good to get more blue presence here.

gdfsgsdfhgsdfghsdgfh

It was a bit before your time. Here is the famous post: http://www.gog.com/forum/general/my_account_big_changes_on_the_horizon/post1.

Toward its very end, it says: " -- Manual sorting is no more. We have decided to skip this functionality because it was beyond our reach to deliver the quality we wanted to. We decided it would be better if we were focused on the numerous other options requested by you. "

As far as I understand it, for all other things mentioned in that post (e.g. Chat, Mobile Device Support) they did manage to deliver the quality they were aiming for.

you cannot change a review... and if you ask to the support to change a review you cannot change the star of the review.

Why change a review?
Because if there is an update that fix a problem I want to be able to change my vote and my review. I want to do that without text to support (also chenge star is not possible even with text support right now).

Also you cannot use gog on a smartphone right now. why don't make a gog galaxy app? it can be really a good thing.