Hey, I got my 15" rMBP about 2 weeks back, but recently tried creating a project on iMovie. I am currently using the base model and I realised that when I create a very movie using photos (10-12 photos) from my photo album, using the comic book theme, and try playing back as a preview (without exporting), the playback is very unacceptably choppy. This issue is not existent once exported. Can those out there try it out and let me know if they experience the same thing? Would love to hear from the rMBP owners with DGPU too to determine if it's a GPU issue or just...an overall issue. Thanks in advance!