During the past ten years, I've stored my digital photos at least a dozen ways. Most recently, I've been using Lightroom because it would catalog the original raw files and all the adjustments. Unlike Photoshop, it makes nondestructive adjustments. I can make a JPEG copy today and make another identical copy 5 years later without storing the JPEG separately. This allowed me to store all my best photos in one place. It also significantly reduced the amount of space required for storage. Best of all, it stored all the data about the photos, including all the adjustments I made. I use Photoshop less and less with each Lightroom upgrade. It's become the most important piece of software I own.
No software is perfect. My biggest complaint with Lightroom was the number of things that could happen to my photos without my knowledge. For example, Lightroom makes preview of the photos I import and then deletes the previews later. Lightroom can lose track of where my photos are. I can accidentally delete photos in Lightroom without a warning. I've lost keywords, accidentally deleted images, and lost corrections I thought were safe. In most instances, the disaster was my fault - but it was still a disaster.
I recently installed Lightroom 4 and was impressed by the improvements. I'll use Photoshop even less now. I spend most of my Lightroom time with new files so I didn't notice a potential problem until later.
Lightroom stores all the edits I make. If I want to export the photo later, it applies the edits to the raw file and I can export a perfectly cropped and color adjusted JPEG file. Lightroom 4 modified the way that some of the editing tools work. This means that edits I made in version 3 don't look exactly the same in verson 4. It tries to make them look the same - the conversion causes my version 3 thumbnails to take much longer to load. I can ask it to convert the settings to version 4 settings, but I can't go back to the version 3 settings if I'm not happy with the results. I have the tens of thousands of photos in Lightroom so decisions that take seconds per photo will result in hours of work.
This is a DAM (Digital Asset Management) problem that I need to solve.