The post that Greg linked to provides more detail on what's going on here, but I can summarize for the benefit of folks that land in this thread.
OmniFocus 1.7 imports your perspectives from previous versions, but doesn't remove them. If you prefer it, you can download v1.6.1 from
this link and continue to use it for the time being. I've got both versions installed in my applications folder - do the same, and you can get used to the new approach gradually, when you have the time/energy to do so.
The old perspectives interface was very powerful once you learned how it worked, but until you figured it out, it could be a real struggle to figure out how to make it do what you wanted. There were a ton of controls to wade through, and it was pretty confusing that built-in perspectives did things differently than any of the perspectives a user made.
Hopefully, with the new approach, we can make perspectives more consistent and predictable for new users without overly disrupting power-users' existing workflows. (Learning anything new is disruptive, but that doesn't mean that continuing to do the wrong thing forever is the right choice!)
That all said, our ears are open. If you feel like we overcorrected,
send feedback and let us know what/why you need things added back.