Possibly this is due to the current swarm of people switching from Google Reader; possibly this is already planned. But while Google Reader felt quite instant, clicking on a different feed or category, or clicking on 'Mark all as read' takes a few seconds to respond.

The pacman (cute!) appears instantly, but it takes a while to load. I don't know if this is the implementation (is it asynchronous? do you wait for a result from the server? maybe GR updated the UI without waiting for a server result) or just the current server load.

If this is planned or currently being looked at, no worries, I'll wait.