Fit for purpose? It was, but now it's pretty outdated to be used anywhere else but low-end phones. A complete UI rewrite might or might not be enough to make it credible again. We'll see. I've owned various (Nokia) Symbian phones and I've been a (hobbyist) Symbian coder, and all I can say right now is "never again". S^3 and S^4 would have to be pretty damn amazing to change that.