Thank you for your post. If your observation is correct it would explain the slowdowns that some users experience after converting their solutions To FileMaker 12.
Incidentally each field in FileMaker 12 has 4 different 'states': Normal State, In Focus, Hover, Pressed. FileMaker 11 had only one state. If the conditional formatting is linked to each state then an option to disable the three additional states could greatly speed up portals and list views in Filemaker 12.
I have added your findings to 'Scrolling in List view is very slow': http://forums.filemaker.com/posts/715ef37320
Thank you for your detailed post and file.
I am able to replicate the issue, and I have sent your post along with my findings to our Development and Testing departments for review. I will keep you posted as information becomes available to me.
There have been several reports about issues with conditional formatting, and we are continuing to investigate this issue.
Seems like this finding would do a lot to explain why screens with a lot of conditional formats are slow to update in FileMaker 12...