Firstly I want to say that if something annoys me on a gambling platform, I simply leave it for good. Why waste your time on a platform that gives you bad vibrations when there's so many great gambling platforms around?

Now, what annoys me the most is poor design, bad customer support and unstable working of the site. And I put "poor design" on the first place not accidentally. More often than not if a platform has poor design, all the other problems will follow.