BA Premium Economy - aka "World Traveller Plus" is a reasonable product ... However it's definitely more "economy class plus" than "business class minus" ... Seats are slightly wider (8 across on a 747 rather than 10) and have significantly more legroom than economy class (38in seat pitch rather than 31) ... Service is the same as economy in terms of food and drink.
It's perfectly fine for a day time flight.. but on an overnight you're not going to find it much easier to sleep than in Economy class
Worth a small premium in my opinion over economy fares.. but not a large premium