Have been using the 'E Tickets' for a few years now for the cruises.
I don't have to log in and out as you do although it's not with Thomsons.
I checked in online awhile ago and have printed my e tickets although I always double check a few days before to make sure nothing has changed.
I can book and pay for any excursions we want to do, book seating in one of the speciality dining rooms for day/time etc
I also filled in and paid for our entry documents into America.
Last week I selected the aircraft seats and paid for the upgrade - all online.
Have never actually checked in on the flight the night before as I'm not too sure how this works