I've been using Lightroom 4 since it's release several weeks ago. I have to say that I love the new algorithms, and I love what it does to my images. There is really only one complaint I have about Lightroom 4.
I have been spending a lot of time going back and re-editing images or editing images I would have otherwise not attempted to edit. Hours and hours have stacked up looking through my archived images. The thing that keeps me going is that I am finding a lot of gems!
Am I really mad at Lightroom? No, not really, but I have been looking back at some of my old libraries and editing images I haven't attempted before, and they are coming out great. The new algorithms, the black, white, highlight, and shadow sliders are amazingly good.
Here's an image I made July 2011 and didn't even attempt to edit it, but once I got it into Lightroom 4 I was able to produce an image that I am pretty happy about. What do you think?
If you haven't tried Lightroom 4 I highly recommend you do. You can download a free 30 day trial from Adobe's website to try it for yourself. That's all I got for now, so I guess I'll go back to combing my inventory of images to see which ones will be next for a Lightroom makeover.