GIOVANNI LANZANI  This is just an amazing little piece of software, I thought the only way to go with this thing was datathief, which is an ugly, slow, buggy, expensive piece of software, but then I stumbled upon GraphClick.

If you need to take data from plots, go for it.

The only minus is that it doesn't state clearly the limitations of the shareware version, so when you find them out, you have to buy it, because it is extremely well done.  
(Version 3.0)

GRYPHONENT  No update for over a year. The other developers apps have either been sold on (PhotoPresenter) or discontinued (the excellent and unmatched ProVoc, which is sorely missed). I am therefore hesitant to pay $8 for this app. Granted, it is a nice piece of software. But I only support shareware that is in active development. And I do not get the feeling that Arizona Software is still around.  
(Version 3.0)

WILLIAM SCHAFF  Graphclick is one my favorite Mac apps. It is as valuable to me as some very expensive apps like Labview, Igor Pro and the MS office suite. It's a bit surprising it doesn't have more reviews, but the reason might be that this app is the one to reach for at the start of a data crunching project that gets forgotten by the end, because it performed its task so well. I think I've been using this for 3 years or more. Every now and then a startup message informs that an update is available. I haven't run into any problems that required an update to fix, but I install them anyway and continue to have trouble-free performance.  
(Version 3.0)

0157H7  In the middle of a really difficult late-night review of some of my predecessors work, I needed to convert some graphical data back into "real" numbers. After much shopping around, I ran across GraphClick, and it saved my bacon. The $8 shareware fee completely belies how useful and well-written this program is.  
(Version 2.9.1)

SANDRIFT  Note that help files do not correspond to 2.4b1 version - keyboard shortcuts are not the same; axis deformation tool doesn't seem to work properly (although I may not be using it correctly because Help is not up to date yet).  
(Version 2.4b1)

ANONYMOUS  Also check out Digitalizer for mac os x (free) at http://naranja.umh.es/~atg  
(Version 2.1)

AHARON DAVIDSON  It is a pleasure to see how GraphClick is becoming more and more professional. It is definitely one of the coolest, as well as useful, scientific applications around. I will pay the $8 gladly; I think it worth much more... In a more 'mathematical' language, 2.2 -2.1 >> $8. One must also appreciate the fact that the developer takes very seriously the feedback comments made by MacUpdate reviewers. All items in my wish list, for example, have been fully and elegantly incorporated. Highly recommended!  
(Version 2.1)

FXT  outstanding. i tested this on several x-y plot images where i've wanted the "raw" data awhile, and this app did a superb job of extracting the numbers. it tool about 10 minutes of playing around with the app to see what it was doing before i was able to get serious about an extraction.

fxt  
(Version 2.0)

AHARON DAVIDSON  Once upon a time, at those glorious days of OS9, there was a cute little application called DataThief by Kees Huyser and Jan van der Laan. I was desperately waiting for its analytic continuation into OSX, but as many others, had to face the fact that it was discontinued. Suddenly, out of the blues, here comes this masterpiece GraphClick to fill up the vacuum. My first impression from this application is fantastic. It works beautifully,and the list of points produced is easily recognized by (say) Kaleidagraph for further treatment.

On top of everything, it is free. We can only hope this nice application will not be swallowed by a bigger company, like another succesful apllication (Curvus Pro X) by the same company (Arizona).

I would suggest however (please add it to my wish list) to control the Automatic curve detection (that is tolerance, spacing, and the total number of points) directly in the main frame, and not to hide it in the references. Furthermore, some support documentation is badly needed.  
(Version 2.0)