Hey cyberioten,
There are some performance improvements we’ve been working on for 9 that are currently available as a release candidate. Can you give build 3650 a try to see if it helps with the issues you’ve been seeing? You can download it at Axure | Release Candidate or via Help > Check for Updates in Axure RP when “Include beta channel builds” is selected.
We have seen that using a high resolution monitor was making an impact on performance (which should be addressed by build 3650), and this was particularly noticeable the larger the window size of Axure RP was. Does this seem to describe the setup you use as well? And do you make any adjustments to the window sizes when running RP 8 and 9 at the same time?