This is the first pro-level Adobe app to hit the Mac App Store. Well, unless you count Elements, but ew. Also, this is the best installation process you’ll find for an Adobe app.
I use Lightroom 4. After Noah was born I realized I needed a better photo editor on my Mac besides iPhoto. I gave Lightroom 4 a trial and it’s great and surprisingly easy to use even for a guy like me who does light photo editing with the pre-set filters.