The answer of course, is, it depends!

IPhoto, and I guess you have version 11, is now quite powerful. It is worth spending time to find out everything it can do. Personally, I find the tutorials on the Apple website to be excellent - go here -http://www.apple.com/support/iphoto/. The mini videos are very helpful and can be downloaded for later consumption.

In the past I used to use Photoshop for most of my personal work and, in fact, used to teach it at Certificate II in Multimedia level. However, I now use Aperture and find that it meets most of my needs. Like Lightroom, it is excellent for organising your photographs and is able to handle RAW files very well. In short I find I can do virtually everything I need to do in my workflow, such as straighten pictures, bring more detail into shadows, tone down burnt out areas, produce great slideshows or digital books, etc. Again, visit http://www.apple.com/support/aperture/ for lots of tips. I now find I have to change into Photoshop rarely, e.g. if I really need to use layers, remove things from the background, stitch together a panorama or add text to a photo.

Therefore. You should find iPhoto will do most things well and will satisfy the needs of most people. If you are more demanding, and particularly if you use RAW then it is worth paying for Aperture and you should find this handles your workflow extremely well. If you really want to try tricksy things then you will need Photoshop CS5 as well.

Lightroom is an excellent product but I find my preference for Aperture is partly because it is extremely consistent with the whole Apple experience which just makes life and learning easier. There are also other excellent photo editing programs but I believe Photoshop is so far ahead it's worth paying for. Having said that, Photoshop Elements is excellent value and has the advantage that if you ever find you need to go beyond that and really use 87 different layers then all you have learnt will transfer into the industry standard product.

Now about a bigger screen .....

Enjoy

Graham