iMovie exports fine for most users.
Slow exporting can be caused by a number of things. If you export at Best Quality (pro res) your export time will be 4x longer. This is because of the much larger bitrate. A slower processor, such as an i5 CPU versus an i7 CPU, can increase export times. Exporting to Theater, particularly when it's simultaneous with exporting to File, can slow down exporting time because Theater renders in several formats to accommodate different devices. Competing activity by other apps can cause a slowdown. Although not common, sometimes when your System Management Controller needs resetting, that can cause slow performance. Finally, some projects, for whatever reason, export more slowly. Try exporting your media from a newly created project.
Address the above issues and see if you can improve your export speed. I would start by doing the following:
Restart your computer and open iMovie while holding down the Option an Command keys and selecting to delete preferences in the box that appears. iMovie will open in a new library. Reopen your old library to get back to your projects. Now see if your import speed increases.
Boot up in Safe Mode (see the Finder help menu for instructions) and, after everything loads, immediately shut down and reboot in normal mode. Then open iMovie and see if your export time is faster.
-- Rich
