My two biggest complaints about Wuala is that its client is written Java and occasionally eats up all my memory (even with -Xmx256m, though I believe this is Java's fault rather than Wuala), the interface is a bit hard to understand and there's no background mode like how Dropbox stays on menu bar in OSX. Apart from these two complaint, I'm pretty happy with the service enough to delete my (paid) Dropbox account for equivalent package on Wuala.