This is going to change wildly with the tax change for suppressors and SBRs. I don't know how, but I think there will either be a huge backlog from people registering, or it's going to be dropped completely. My bet is on dropping it, I don't see the ATF having the manpower to process the volume of forms... keep in mind, you can register if you even intend to make the weapon/device, so I've seen people readying dozens of forms ready to submit. That, times the millions of users waiting for the tax to drop to zero, is going to change the landscape significantly.
That said, I'm looking forward to it. I'm just waiting to make a run of Red Bull can .22 suppressors!