Lightroom always drives me nuts, it just throws too much information into my face, but you can get used to it. The mass-editing is perfect there, though. Still, I prefer photoshop.
Paint.NET is a great idea, fast and reliable, but not really for photo editing. Well, it can be a good photo editing software if you get some addons. But what I like in paint.NET is that it's really fast, and of course, that it's using Microsoft .NET Framework (I'm a .NET software engineer )