I use them regularly. Dont have any complaints. As you note, Speedy Boarding (Fast Track) is rigorously enforced - which is good.
The seats are better than the new BA Pinnacle seats. Note that the OP paid for seat selection. Row 1ABC seats has no bulkhead and you can stretch out.
Best of all the "seat shifters" have never moved me on EasyJet, whereas BA move me all the time - including out of 1C on Friday.