Laggy Performance with Rulers turned on
Enabling rulers degrades AI performance, especially with regards to Smart Guides and object mouseover highlighting.
The effect is the same whether GPU preview or CPU preview is used.
Attached is a sample file with a few hundred rectangles.
With Rulers off, mousing over the objects results in immediate highlighting of every object, and immediate Smart Guide anchor/path annotations.
With Rulers on, mousing over results in missing highlights - AI can't keep up and only displays highlights and annotations intermittently.
The original post appears to be correct. I am trying to use Version 23.0.3 with GPU Performance Enabled and turning off rulers does appear to boost performance/response time in Illustrator. Currently I am bouncing between 23.0.3 and the latest 2018 version of Illustrator to deal with ongoing performance issues of software.
Kevin A. commented
I've been experiencing this same problem since the initial Ai2015 release. Seems to continue on in the latest builds for me as well.