I read good reviews for panelbase, it was even at the top of some survey lists. However, my experience with them has been the opposite.
Very, very few surveys in comparison with other survey sites like valued opinions or mysurvey. There is a very tedious profiling section to be completed at the beginning and it's all for nothing. Most of the time I'm not even eligible for their surveys, yet they give them to me anyway (at most one per week).
Terrible site and an absolute waste of time. Avoid.