Presumably, ticket sales will have gone "well" in that there will be a core of people (like me for example) who go most years regardless of the line-up. But That core of people might well account for less that half the capacity, then they need to convince people on the strength of the lineup. I think Thursday will have sold well, the others less so. Unless something good drops in the next announcement then I will be very surprised if all 3 days sell out.
My first PKP was 2010, top names on the poster were Iron Maiden/Placebo, Snow Patrol/Prodigy and Queens of the Stone Age/2 Many DJ's. So Good, OK, and Meh in equal measures really. Lots of strength near the top of the lineup though. Interestingly (for me at least) looking back at the older posters it was more clear who the headliners/big names were. I googled Pukkelpop 2010 and looked at the first result in images, then Pukkelpop 2014 and looked at the first result in images. 2014 very confusing, alphabetically arranged and making it very difficult to determine who is what (other than font size).