This has replaced a large number of mail rules I used to have - and more importantly, the time I spent maintaining them. Also adds a bunch of functionality over and above what mail rules can do (even using imapfilter).
However, there is a fly in the ointment. With push notifications, I frequently get notified of an email arriving before Sanebox has a chance to 'see' it and files it away for later. So I get a lot more 'nuisance' notifications for emails that Sanebox decides isn't important a few moments later. In other words, there's a race condition between email client notifications and Sanebox processing.
Their support folk are aware of this, and their workaround is to turn off push notifications. I wasn't impressed.
I've suggested that they add the ability to configure which folder they consider is the 'Inbox', so I can write a single mail rule to put incoming mail there. Then Sanebox would see the email before any email clients, who would continue to monitor the actual Inbox.
That way I'd only get notified for emails that Sanebox determined should be moved to the actual Inbox from the secondary one. However, I don't know if this is something Sanebox are considering - the support person said they'd pass the suggestion along, but given how long sanebox has been available, I can't believe this is a new idea to them. So I'm not holding my breath, and I'm still looking for either a way to work around this, or an alternative that doesn't have this flaw.
