1. Notification of updates comes up in the systray 2. Clicking it, Discover opens saying "Updating" 3. After long time (e.g. minute), it still says updating 4. Switching to konsole and doing sudo apt-get upgrade takes about 10 seconds to complete (fast internet and SSD drive)
Could you try running the update and in parallel execute pkmon? Maybe you'll be able to see what's it spending the time on. In any case this is dealt by PackageKit and your distribution, there isn't much Discover is doing there.