Dear Tom, we are suffering the same issues on our site.
Netflow stopped working since we upgraded and now we have to enable the accounting on thousands of rules , something that was not required at all in R80.10. this doesn't make any sense even when they are going to revert back this feature in R81, meaning that the accounting won't be required to get Netflow working.
Checkpoint, before performing these behaviour changes, you should think on the fact that these changes are causing a huge time consuming for your customers and not only this, but also the high performance impact it has on the MLMs.