As a beginner, I chose to get Apple's Aperture 3 because of my familiarity with Apple programmes. I love it, and would be perfectly happy with it, if it were not for the fact I know no one else who uses this software, and the online tutorials have taken me as far as they can. As a learner I am far more effective when I am shown one-on-one, and I have stalled in my efforts to use Aperture to its potential.
So I have now purchased Photoshop CS5. Now to find someone, and some time, to learn to make the most of this software! I do have a conference workshop coming up to get me started, but I imagine it will not necessarily be only about photographic post processing... however next year it is a goal to really learn how to make the most of it, via a course or something...
In the future maybe I know enough to play with the big boys in Lightroom.
PS Grateful to be able to purchase at an Education price, which allows installation on one work machine and home machine as well :)