Most of our passengers want allocated seating and have done for a long time so IMO Easyjet are giving those passengers what they want. Read flight reviews and many, if not most, will comment on the free seating even if the rest of the flight has been excellent.
Now, my personal opinion is that on paper free seating should work just fine....it does on a bus or a train but throw in some (mainly) leisure destinations, very busy/full flights and things can be a nightmare. Despite that, the crew do a fantastic job and the level of disappointment amongst pax regarding seat arrangements is usually no more than allocated seating. The fundamental problem is (and this sounds really patronising) that a huge swaithe of the air travelling public just cannot relax and/or see logic. i.e a flight usually has to be well over 90% full before people have to sit apart. Consequently they can be edgy at best and like a pack of animals at worst.
Even if people book fairly late on I honestly think seat selection won't be too much of a problem. Extra leg room are limited regardless of how you allocate or board a flight and many legacies allow seat selection at the time of booking which is no different.
Many cite the business passenger as the ones losing out. From experience these guys tend not to care too much about where they are sat, not least as there is little difference anyway. I think I've also mentioned in the past that often on business type routes, there is seldom a scrum for the extra legroom/exits. Plus with City routes there are a higher percentage of single and couples travelling and therefore that takes the pressure off somewhat and as a consequence, fewer will opt for paying for seat selection.
Meanwhile on leisure routes the option will be very well received and whilst i would anticipate the majority to take advantage of this, there are always those people who choose to risk it, not willing to pay for it or where seat selection just doesn't matter and this will balance things out somewhat.
I am not entirely sure what will happen regarding Speedyboarding plus but I can foresee some type of "perks" package in some way, shape or form but I guess we will wait and see.