In addition to the reasons Corky02 listed (how much RAM and what kind of processor do you have,BTW?) Aperture may become slow, if your hard drive fills up - keep more then 20% of your hard drive free.
How long have you been using Aperture? If you are just starting to use Aperture and doing the initial setup of a large library, Aperture still may be busy with the initial processing of thousands of images. It will be much more responsive when this initial processing and indexing has been done.
You may wish to turn on Aperture's "Activity" viewer while you observing an an natural slowness - so you can see what tasks are performed and watch the progress. You also may pause tasks (indexing Faces, creation of previews), that you want to postpone and rather run over night. The Activity viewer can be started from Aperture's main Applications Window:
Window -> Show Activity
Two more diagnostic utilities (from Applications -> Utitilities) are useful: the "Console" and the "Activity Monitor". These will show you if any processes are crashing or logging diagnostic messages, and also how much processsing time Aperture is using, or if other processes are competing with Aperture for processing time.
Apart from the initial import of a large library Aperture may show slowness if you have a serious problem with your library:
- You may have imported a corrupted, incompatibable image
- or your library got corrupted (maybe by using a drive not formatted MAcOS X Extended, or by Force Quitting Aperture).
Then the Aperture First Aid Tools may be able to fix this: Try to repair the permissions and to repair the library, as describe here:
Aperture 3: Troubleshooting Basics: http://support.apple.com/kb/HT3805
Report back, if this does not help.
Regards
Léonie
