I am definitely no expert in image editing, rather a rookie.. But I found this quite easy to use with lots of presets and the possibility to up/download more on the website.
Seems quite light on resources.. I have a Dell E4300, Win XP and 2GB memory, and the software is really quick.
My favorite function is the before/after with a split view where you have half of the photo in "before" and half in "after" when doing adjustments. This might be a function in lots of other software packages, but I warned you that I am a rookie..