...there are many factors that influence application performance. I actually have the exact same mac setup as yourself, however i run 6GB memory. Memory is the single most effective upgrade you can do to enhance performance of Illustrator and applications in general...
...faster saving and smaller files sizes from illustrator can be achieved by turning off the PDF compatibility option in the "file > save as" dialog.
...even with this option off however, there will be a limit depending on artwork complexity to how file sizes perform...
...the other area that illustrator will display slower performance is with regards the "document raster effects" setting, found under the "effects" menu, in conjunction with artwork effects such as drop shadows, glows etc, that require bitmap data to be created...
...the raster effects setting defaults to 72dpi usually, so cranking this up to anything higher than 260dpi is not only too high, but has no advantage in both performance and print quality come final output. In fact you can do well in high end printed output with just 150dpi...
...the sprayer tool bases itself on "symbols" which help to reduce file sizes and also performance, so looking at your outline preview posted there is certainly a lot going on there, so I wander if many of those areas could have actually been created using less areas with the sprayer tool. The tool does allow you to add to existing areas, but without seeing your actual artwork, dimensions, resolution used, effects etc, it would be difficult to determine if anything can be changed to improve illustrator performance...
...there is a kind of myth with vector artwork producing smaller file sizes than pure bitmap work, in some cases this is true, however there comes a point where pure bitmap data actually performs better. This is not only true with printed output speed, but also with regards PDF export...
...having said that, vector work produces sharper and cleaner printed output, so the advantages kind of outweigh the costs in my view...
andrew
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