I have a iMac 3.4 Ghz Intel Core i7, SSD 256 root drive and a 2 TB secondary with 16GB of memory. Three weeks old with Lion installed. I have a Keynote deck with 21 slides. Some text, 2 videos 144MB each and 1 560Mb movie. Entirely new deck and the progress wheel spins every five minutes for 30-40 sec. Tried all of the good suggestions above and no changes. Checked the activity monitor and CPU is under 5%, system memory available is 15GB, Disk activity appears normal. However checking the logs do find event hang which lasts for .40s
Those of you having issues might want to copy your system diagnostic report for keynote and send to apple support or force quit and send to apple with your comments.
I also work on a MacBook Air i7 and not seeing the same behavior with 4GB of RAM and SSD nor seeing the same console errors using the same file. Hard to replicate across both devices.
I did get one interesting error message yesterday that told me to close down some applications (only had two open) saying my disk space was low (swap) on startup drive. That was interesting considering have 179GB free and nothing showing on activity monitor.
BTW have run repair disk permissions, removed keynote .plist with to no avail.