I finally had the system working the way it was supposed to on 2 relative empty flights. Both time I had a whole row for myself which was nice. Actually on the second flight I was the only passenger in 4 rows except 1 Virgin pilot that was free riding (probably got stranded with the weather).
The FA's did also not allow seat poaching into those 4 rows.
I still find it more of an annoyance then a real gain, it is a little more legroom but I am still annoyed not being able to get seats in the front anymore at booking. Those 4 rows are blocked and row 5 has the isles blocked, so first possible is row 6.
Also I do assume that the 15$ / 25$ price difference are low enough to have business travelers pay for it to get a better seat when they check in online. The web site now pushes the up sell to stretch seating pretty hard.