Tickets for the WGW are very expensive compared to other international Goth festivals where you get to see bands all weekend for about the same price.
The quality of the event depends on the bands they've got playing but make sure you arrive early because, even if you've bought a ticket, you may not get in (due to venue restrictions on numbers).
If you don't buy a ticket you can still enjoy the weekend as there are plenty of cheap/free events that you can go to during the evenings and lots of stalls/shops to look around during the day.