Hi
Marcel,
Your ideas and mockup look pretty nice! Let me share my thoughts on this.
The first that I noticed that orange icon in the bottom right corner is too bright, and users always will focus on it and clicking "Mark All As Read" will become commonplace action. For example, I am not so interested in news but I don't want to see such bright element.
Another thing, I prefer to separate categories: Updates/Marketplace/Planet. Updates category is the most interesting for users. They will see something like "EGit new release", or "JDT new functionality available" in the menu. And after clicking on it, the additional dialog will be opened with details about update and magic button "Install Update".
I like your idea about notification popup with new updates, but it should be implemented carefully. The dialog should contain such buttons as "Skip", "Install", "Remind Later". The interval between updates notifications (not news) shouldn't be less than 1-2 days. And if user skips some update, he shouldn't see it again.
Good progress!
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Best regards,
Igor Zapletnev