After almost 1 year of waiting, I recently upgrade to the latest and greatest i7, 680MX graphic card, fusion drive iMac. I assumed that I wouldn't be left waiting to switch between projects, or events in iMovie. BUT, to switch between projects that are only 1-5 minutes long takes about 1-2 minutes. I have only 4 projects. I thought to reject a clip would be instant, but it takes 5-10 seconds to simply remove a few seconds of clip (or entire clips) from the browser. Thumbnails do not appear instantly 2-4 seconds, which slows browsing events. On the apple site, the problem is known since 2010. There are only user led solutions, which are workarounds, not solutions, and do not work practically for me. I certainly see faster times if I switch to a smaller event, and then change projects, but I then have to re-open the iPhoto library, and refind the clip I wanted. Super, I upgrade the hardware, and it reveals the problem was in the software. I noticed that iMovie now imports the video content from my camera. Perhaps this is part of the solution (ever optimistic).