CS3 Extended version includes many new and interesting features. Now it offers intelligent filters, a new system to edit layers without having to duplicate it,...
Another interesting feature in Adobe Photoshop CS3 Extended is the possibility to select an area quickly by combining two functions: Quick selection and improve borders.
But these are not the only ones, you can find a good number of new features in the section 'advanced composition capabilities'.
Don't hesitate, Adobe Photoshop is the most famous image editor and there are lots of reasons for it. Try it, you will not be disappointed.