Probably more RAM will help. If your Mac is not maxed out with 4GB RAM go for it.
Have you checked with Activity Viewer (in Applications > Utilities >Activity Monitor.app) how much RAM Aperture and other Applications are using, also how many disk outs?
Another reason for a very slow mac when Aperture is running, may be an overful System drive. If your disk gets full (less than 10 GB free space) the decrease in performance will be dramatic; you should keep more than that free.
The article you pointed to, names many valuable trouble shooting measures, but recreating your library is wasteful, also deleting all your presets, if are not sure, what the problem is. Try to narrow down the problem, before sacrificing your presets or your library.
When did this problem start? A gradual decrease in performance may be due to insufficient hardware, RAM, disk space.
One or more of your projects may be too large. Your library may be gigantic, but keep the projects small.
Your library may be corrupted; this may happen, if Aperture crashed or you force quit the application.
Have you tried to repair permissions and to repair the library lately? If not, then try that as a routine maintainance measure.
See: Aperture 3 User Manual: Repairing and Rebuilding Your Aperture Library
You may have imported one bad image or video, that Aperture cannot process. This will typically cause Aperture to hang on launch, trying over and over again to process this image or video.
In that case it will help to hold down the shift⇧ key while launching Aperture. Then it will not try to render previews for corrupted images.
If Aperture is wasting time "Importing" on startup, this may be caused by imports from web journals (Facebook, flickr, (shared) Photostreams) and rendering previews and scanning for faces. If you do not really need these feature disable them for a while.
Or is your Aperture still trying to connect to Mobile Me? Then remove all references to Mobile Me from your system , if you still have MobileMe in your Aperture Web Preferences.
You can check, if your Aperture Library is causing the problem, by creating a new, empty Library and experimenting with it for a while.
And to make sure, that none of your presets and preferences in your user account are making trouble, open Aperure in a different user account: create a second user account from the "Users&Groups" preferences panel and launch Aperture from this new account. Import some testimages and see what happens.
Does your Aperture Library contain any smart albums imported from iPhoto? And where is your library located? On an internal or external volume? Referenced or managed?
Regards
Léonie