It's tough to catch up with Mathematica when you guys keep putting out such awesome stuff with each new version. It's been great to see Wolfram innovate so much – versions 6, 7, 8 and 9 were all amazing releases (especially after the four-year gap following 5). I found the new symbolic discrete calculus work in 7 and the symbolic statistics capabilities that built on that in 8 to be particularly mind blowing [1][2]. This seems like it was the fruit of a focused, long-term R&D agenda.

Regarding Julia, although the syntax is superficially similar to Matlab and we've intentionally made many things compatible, Julia isn't really modeled on Matlab. Julia is much more influenced by Lisp – much like Mathematica via Macsyma and Maclisp. Julia's dynamic multiple dispatch is somewhat reminiscent of Mathematica's pattern matching dispatch system too, although, of course, the evaluation semantics are radically different.

I hate to quibble, but having a web frontend for Mathematica that you don't charge people to use does not make it "effectively" open. Mathematica is a shining example of excellence in closed-source software and I have no problem with it as such, but calling it "open" because there is a web version is just disingenuous b.s.

[1] http://www.wolfram.com/products/mathematica/newin7/content/D...

[2] http://www.wolfram.com/mathematica/new-in-8/probability-and-...