AN.ONYMOUS  This is not a demo, just a marketing trap for catching information and email addresses for potential customers.

MacUpdate should bane this firm.  
(Version 7.9)

THEDOWD  EEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE  
(Version 7.9)

CLAUCLAU  Can you believe it, you've already finished C, think you can do Matlab?  
(Version 7.9)

AN.ONYMOUS  The "Free demo" is only for registered users.

Other people have to fill a detailed request. Then they are told that "A MathWorks representative will contact you to discuss your needs and provide access to trial software."

I know what I need : a free demo not a discussant about my needs !  
(Version 7.8)

XPLICIT  On this webiste under price (start page, price column) it says free, but the download link directs to Mathworks' website where they state that it's only a 15-day trial for free. And when you try to look up the price there's a login required. What the ...? I just wanted to know how much it is. Download of the trial also requires a login.  
(Version 7.8)

TAOEFFECT  This software isn't for people looking for a shiny Cocoa-application. It's for people looking for a top-of-the-line mathematical and computational tool. I've yet to come across any software that can compare with Matlab in this regard, it's amazing.

Its language is very easy to work with, well designed. People with limited programming experience should be able to pick it up easily.

The built-in documentation is top class as well. I've compared it with Mathematica's documentation, and it blows it away. It's easy to search, comprehensive, and the examples work.

Matlab makes it painfully easy to manipulate and visualize data, and run various experiments. Its full capabilities are rarely tapped, as it can even integrate with various other languages. If you're looking for a product that makes it easy to do hard things, look no further.  
(Version 7.8)

GREGWELCH  Among other things, R2008b makes Matlab an OS X package, so it looks like a "real" OS X application.

"Value" (rating) is hard for me to judge because my university has a site license.

While there are things to complain about, I for one am very pleased to have it on the Mac, and working quite well (albeit a little clunkily) for my needs.  
(Version 7.7)

MARK EVERITT  Another suggestion is Octave. It's extremely close to Matlab (especially since version 3) and all the code I have written now runs in both. The best part is that it's free!  
(Version 7.7)

MBHOCKEY  When is this going to be native? X Window is horribly slow.  
(Version 7.4)

JT42B  If you are unhappy with Matlab or just looking for something simpler you may want to check out MathPad

It's not really on the same scale as Matlab but it's free. It provides a language with array constructs and includes simple visualization. I find it surprisingly powerful and have used it for tasks that others have used Matlab for.  
(Version 7.3)