Lion was known for its memory-heavy "Resume" and "Versions" features. For better performance in Illustrator, consider disabling these in System Preferences.
If you're experiencing issues with Adobe Illustrator on Mac OS X Lion, consider: adobe illustrator mac os x lion
Minimum 2GB (8GB is highly recommended for complex vector work). Storage: 2GB of available hard-disk space for installation. Display: 1024 x 768 resolution (1280 x 800 recommended). Lion was known for its memory-heavy "Resume" and