I use Lightroom only about 99% of the time. Only a very small portion of my images need to go to Photoshop.
I would like to know this too. I bought the first version of lightroom and uninstalled it after a few months since I never used it.
I get that the organization and inline editing abilities would be great if you are starting out with nothing. But I already have a self made rube-goldberg of a file structure/workflow with well over a hundred thousand pre-existing photos which I would have to organize in Lightroom just for starters. My system certainly isn't ideal but it works for me.
Is there something that newer versions of lightroom do that isn't accomplishable with ACR and Bridge beyond the aformentioned streamlined editing and organization?
Are there edits you can do in lightroom that you can't do in bridge/acr/ps? Not really.
The real reason to use Lightroom is for the more efficient workflow and non-destructive editing. Working in Lightroom is a completely different paradigm from using Bridge/ACR/Photoshop from a workflow perspective. For me, the beauty of lightroom is that I don't have to come up with file system acrobatics to track my files and edits. The files are stored in a simple layout and the edits are all stored purely in metadata. Storing only one version of the file in most cases is a great benefit for me.
Another big advantage is the ability to easily process groups of files at once. Mass applying changes like WB, NR and lens correction makes processing a lot faster.
A powerful import/export engine along with solid plugin library to further enhance functionality is another time saver for me.
Working with Lightroom efficiently requires you to rethink your workflow and thoughts around file management. If you are not willing to do this then Ligthroom is not going to be a good option for you.
I don' t use either but our local camera club just announced that one of them is moving to a subscription style service. Exactly what that means I can't say but it apparently had quite a few people concerned about future costs.
Photoshop is what is going subscription only. Lightroom will continue to have a perpetual licensing model.

