I continue to be impressed with Adobe Lightroom. Like Tim Bray, although I prefer open source software, I can't help but like Lightroom.
I was also impressed by The Adobe Photoshop Lightroom Book by Martin English. Usually I'm not that impressed with books on how to use software. They're either reference manuals or beginner's guides. This book is neither. It gives helpful advice, covers both basics and more advanced features, and is full of examples and annotated screen-shots. Lightroom was designed to be "simple to use". But it still has a ton of features, so "simple to use" means lots of non-obvious features - like things you can click on or drag. The book helped me discover these a lot faster than I would have on my own.
One of the reasons I like Lightroom is that there are lots of innovative user interface features. It's not "eye candy" - the UI is very subdued black and grey (after all what's important is your pictures, not the software) Even if you're not interested in digital photography, I'd recommend spending some time with the trial version just to see how the UI works, although you may not discover all the features in a short test. The UI has already inspired some improvements in Suneido.