Added Variable-width stroke (custom stroke profiles), Bristle Brush (natural media simulation, CPU-heavy), and Perspective Grid (1,2, or 3-point perspective drawing). Shape Builder tool (intuitive combine/subtract, replacing Pathfinder for many tasks). Anti-aliasing on GPU preview. CS5 also introduced Draw inside/behind modes.
Integration with Adobe Stock (search/place watermarked images), Team Libraries (collaborative asset sharing), Variable fonts (one font file behaves as multiple styles), and More realistic Bristle Brush using new physics. Trim View (hide artboard bounds). adobe illustrator-versionshistorie
Widely considered the worst release. Adobe rewrote the core to use Adobe CoolType (their own font engine), but it broke compatibility with thousands of PostScript fonts. The interface was bloated, slow, and crashed frequently. Many studios reverted to 5.5. FreeHand 7.0 (now owned by Macromedia) introduced tabbed panels and perspective grids, outpacing Illustrator. Version 6.0 was never released for Windows. CS5 also introduced Draw inside/behind modes