The big seats (If you get them) are for the most part better then a standard economy, and similar to many premium econ seats. However WOW has no issue pushing you out of your seat and dumping you in some middle seat at the back of the plane, even though you paid and confirmed the seat. Be prepared to not have that seat on check-in.
In my case 4 total flights and lost the seat on one (luckily the shorter leg), co-worker 2 out of 4 and another co-worker also 1 out of 4 ... so this seems to be more than a random glitch.
They like to double charge for it, and then go back and forth in hopes you will give up the refund request. I suspect this does generate revenue and overall the Airline knows that it has no need to invest in customer service that is not what is attracting people to the flight ...