[Phanx]

I haven't actually tried the app (and probably won't, as I already get free Curse Premium as an addon author and I don't use many addons that can't be updated through the Curse Client) but based on your screenshots I have a few suggestions for the addon management list:

(1) Add a way to quickly visit an addon's website. A button up there with Browse, Refresh, and Delete would work for this.

(2) Increase the font size, or at least increase the padding (whitespace). People with poor vision and/or high screen resolutions will likely find the current small size and lack of whitespace between text and borders rather eye-straining. The best solution would be to use the system text size setting (Control Panel > Display > "Make it easier to read what's on the screen") and the system font setting (Control Panel > Personalization > Window Color and Appearance > "Advanced appearance settings") with a generous amount of padding, but I don't know what GUI framework you're using or whether it supports using the system settings.

I'm also not really clear on how useful this whole thing is... does it recognize when updates are available for the user's installed addons are? I don't see anything in the screenshots indicating that. Without that feature, it seems like you've put in a lot of work just to spare the user from having to look directly at their AddOns folder or learn how to extract a ZIP file. Am I missing something?