Not all of us can afford the huge price of CS5 from Adobe and fortunately there are other applications for the Mac that will do a lot of what the Creative Suite can do. Maybe if you are a graphics professional then you will have to bite the bullet and get the Adobe product. If you are not then it is worth undoubtedly a great idea to look at the alternatives.
If you are really poor then you can start with the free option which is Gimp. It is a cross platform open source option that I am not particularly fond of having tried it a while back. It could well be better now but in these articles I want to look at the three I have used lately - Acorn, Pixelmator and ArtText. ArtText is a little specialised in that it is for creating logos but it does do some graphics bitmap manipulation that is useful and not so easy to do in the other more general applications.
For example - A drop shadow effect. In other applications such as Keynote and Pages you can easily add a drop shadow merely by putting a tick in a box. Out of the box with Pixelmator you have to duplicate a layer, then fill the object shape with black, give it some gaussian blur and then do the offset to get the effect. There is a Noise Industries drop shadow filter that does do it really easily. You will have to add the FXFactory to get access to the extra filters though.
Another thing I miss seeing in Pixelmator is the ability to create basic shapes easily. You can do an ellipse, circle, square or rectangle buy selecting a shape and filling with a colour to get the basic shape. But what if you want a star shape, not so easy to do. The easiest would be to use keynote and do a copy and paste.
One of the effects I like to use with text is a bevel effect, which makes it look three dimensional. Very easy to do with Adobe CS but needed a quartz composer plug in to use in Pixelmator. It is not as good either so I may use Art Text instead to make that part of my graphic instead. The Pixelmator way has limited controls and is called SuperEmboss. Not that easy to install either, but I managed it somehow.
Despite some moans about Pixelmator it is a very capable application for creating bitmap graphics and well worth having in the arsenal of applications for dealing with bitmaps. It is a beautiful looking application and very Mac in the way it works, which has got to be good. Now have a look at the review of Acorn to see how it compares and also the application ArtText.