First launched in 1988, Adobe Illustrator has an even longer pedigree than Photoshop. And for much of this time its creative capabilities have been effectively circumscribed by PostScript, Adobe's page-description language.Illustrator CS5 is still defined by PostScript - it has to be in order to enable high-resolution, fully scalable vector output - but Adobe does what it can to push the envelope. This time, it kicks off with better control over arrowheads and dashed lines.
The big change is that Illustrator CS5 adds a Width tool, allowing you to drag out from multiple points along a path to interactively vary its width. This neatly sidesteps one of the big limitations of PostScript: that paths can be stroked only at a uniform width.