Under the current act right now, when prior user rights are established between an entity.... Essentially you've used a technology without any knowledge that someone else had subsequently invented it. You've been using it and it's fundamental to your business. Right now when that patent is ultimately granted, the law requires you to cease any use of that patented technology, which usually requires you to cease operation. Essentially you end the practice even though you had previously established the capacity to use it independent of knowing that someone else was subsequently patenting it. This would allow you to continue to be able to use that under your prior user rights.
The notion is that you and I are both independent business people. We both come up with the same idea. Prior user right is nullified if I actually did know, if I had been secretly googling you and finding out that you had actually also been taking this action, but it essentially prevents me from having to cease my operations, because I had established prior user rights to the technology, absent knowledge that it was patented.