SERO-P "includes" the newest $10 smartphone fee. An Android/BB/Instinct-type device would be $40/mo for current SERO users or $50 if that device has "4G" in its name (as of this post). So you'll only be at the $50 mark with the EVO/Epic/Transform/Shift.
Where it gets interesting is how some SERO users aren't getting charged any new fees for activating smartphones. So a new TP2 activation on SERO should stay at $30/mo. Then you have the SERO-restricted devices that pushes you into SERO-P at $40, as well as the 4G phones that go to $50. That is unless it's an insurance/warranty/repair device, in which case you're not affected.. until you contract renewal date.
They could probably have made this a little simpler
And for everybody posting about my Sprint Nav/TeleNav rant.. please go back to my original post and read the signature in that post.