I find clicking on the tabs e.g. planner or activities or teams etc, there is a bit of a delay, unlike normal desktop applications. you see the spinning wheel for 5-10 seconds and sometimes it simply fails to load. clicking the tab again then magically works. If you switch away and come back you go through the same 5-10 second delay again. I understand the desktop application seems to just be a shell for what looks like web calls, but if you design the application as a desktop experience, then it should perform like a desktop experience.