any substitute of photoshop??

It's worth mentioning that the review is already a year old. I believe that he's talking about a version of the Gimp that has already been superceded. My copy certainly seems to have some functions that he says are in development. As you can see, whether you choose one or the other depends on what you need to do with it. You would hardly go out and buy an architect's drawing pen merely to write shopping lists ... on the other hand, if you have one in your pocket, it will do the job. You are lucky that you have Photoshop, perhaps. Personally, I found it too complicated and prefer Paintshop Pro (which is cheaper) but find the Gimp loads a lot quicker and, together with Inkscape, does all the things I need it for.

Here are some Gimp tutorials that are probably worth playing with: http://graphicssoft.about.com/od/gimptutorials/GIMP_Tutorials_Learning_The_GIMP.htm

Luvuman mentions Inkscape, another excellent freeware/opensource GNU project. Inkscape is a vector-based graphics program, with more similarities to Corel Draw than to Photoshop or the Gimp (which are bitmap editors with some vector capabilities). Inkscape and the Gimp work very well together. I might use both, for example, in designing a logo. One of the tasks I use Inkscape for a great deal is in tracing a bitmap to turn it into a vector graphic (a collection of lines and filled objects). As you probably know, if you have a small bitmap picture which you need to enlarge by several hundred percent, you cannot go very far before it becomes 'blocky'. One solution is to use a 'tracing' program to select the elements of the picture and turn them into a collection of 'objects' which are defined by 'paths' and can be printed at any size you want without any loss of detail. This works best for line drawings and rather simple bitmaps. You can achieve interesting and artistic effects with photos but the result is a simplified representation - something like posterization.