Forgive a noob question, please! I've never used Lightroom (and am wondering if it's necessary for me, since I'm a beginner/hobbyist who doesn't shoot large numbers of pictures). Can't you correct the WB in pretty much any program? I've mostly used PSE (have version 12 now) and it lets you remove a color cast/change the color temperature. Isn't that what WB is? Is the advantage of LR that you can apply the same correction to a whole batch of photos at once, or is there another reason that LR is better?
Yes, pretty much any program will work. Google Picassa (free) will even work.
But, here's the thing. Are you using a JPEG file? That file has been compressed, and in that process some of the original data has been lost. You edit it and then save it as a JPEG again. More data is lost. This can cause visible artifacts in the file. You will get less smooth changes in colors, things lilke that. If you're using PSE to edit a RAW file (through Adobe Camera RAW, which it includes), you won't have this problem. If you shoot in JPEG and your white balannce is way off, your results will not be very good (trust me, I've been there). RAW also lets you adjust brightness/contrast far more than JPEG does without losing detail. Sure, we all want to get the exposure right in camera, but when you don't RAW gives you much more room to fix it after the fact.
LR also has a much better organizer than PSE does. The PSE one seemed pretty basic when I looked at it. This is good for sorting our photos out. As you surmise, LR can easily apply a set of changes across a batch of files. It can also do batch exports (say you want to upload a bunch of lower resolution files to Facebook, it can do that for you). LR is non-destructive too. It does not modify your original file, just applies a set of changes to it that you then export as a different file. You can do multiple virtual copies to try out different processing (Save as.. in PSE can do this too, of course) I don't remember if PSE automatically saves the original file or not. If not, it's always a good idea to keep your original around so that you can go back to it if your edits go bad (yup, been there, done that)
LR is not necessary for anyone. There isn't much (if anything) that it does for processing that ACR + PSE can't already do for you, but it makes some of that easier. If you use a MAC, Aperture is supposed to be very similar. Corel Aftershot is similar as well (and pretty cheap too, I got a free copy on sale a few months ago, but haven't used it). There are some freebies as well (Darktable, RAWTherapee, Lightzone, probably others) that are supposed to be good as well. The biggest advantage to LR (and, to a lesser extent Aperture) is that so many people use it, there is lots of help out there. Books, magazines, online training videos, online articles, etc. The other tools have much less of that support, and may also be a little slower to support new cameras.
I hope that help a little. I was slow to switch to LR, and went through many, many workflows until I got there. All had some good points, but they all have flaws (even Lightroom & Photoshop). That said, I wouldn't go back now. LR is, overall, the easiest and most powerful tool of the ones I have used.
