For me the real achievement of Wolfram is the visualization capabilities. The knowledge bases are nice if you happen to be interested in a domain that is represented, and they make for great (controlled) demonstrations, but Wolfram Alpha (which taps these same knowledge bases) really fails often when making arbitrary but reasonable queries.

I think Wolframs visualization libs set a high bar, though, and I hope non-closed communities (like the python scientific/mathematic programming community, the R community, etc) will rally to meet the challenge.