I'm no expert but I'll give you my experience. I may have over egged the pudding on some bits as It's still new to me, but I'm sure I'll be corrected if that is the case. The bet thing I can suggest is to download the trial and give it a go.
I have been using Bridge and Photoshop to do everything for several years with my D80 images. 95% of my time in photoshop was spent adjusting raw files, cropping, rotating, resizing etc. A huge waste of the software but I had an old license so I used it.
When I bought my D7000 and started shooting in RAW on it I found that my version of Camera Raw couldn't process those files. Wanting to look at the images fairly sharpish I downloaded the trial of Lightroom 4.3 from the Adobe site. I too had seen it mentioned on the internet in various places and the gentleman I bought my D7000 from also mentioned that he did most of his pro work in Lightroom while only dipping in to Photoshop on occasion where needed.
3 days later I walked into my local Staples and bought Lightroom 4 for £80. My wife then ran away with it to wrap it up to give it to me the next day for Christmas! (We had our Xmas day on the 23rd due to work)
Lightroom will allow you to manage your photos, do all the keywording, flag and rate images, create smart collections (show me all photos with "sunset" in a text field, or with an aperture of f/2.8, or taken on the D7000 and with the 50mm f/1.8 lens).
It also uses the same version of Camera Raw as Photoshop, so you can still do all of your RAW processing non destructively. If you want to copy the same settings to multiple photos then it's just a few clicks away. If you don't like any of it just hit reset. Create a virtual copy of your RAW file so you can perform multiple edits and compare them side by side. You can also use the graduated filter and brush options to layer on different RAW conversions to different parts of the image.
When you want to export your images just select them and tell it to go do it and it'll let you set a max size, apply watermarks, rename, apply extra sharpening etc. You can also upload directly to Flickr or Facebook or other services if plugins are available.
It also has 4 sections I've barely used (I've only had it a few days!). Map, Slideshow, Book and Web. Map allows you to geotag your images using Google Maps, Book allows you to create photobooks with various layouts and text and whatever. It uses Blurb as the printer and will give you a running approximate total as you go, or you can export to PDF if someone else is printing it. Slideshow does as it says, though I'll never use it so have not looked at it. Last is the Web module which allows you to create web galleries in a few minutes. You can choose different templates, make your own, buy them from others, preview the final result and then upload directly to your server or just export all the required files to a folder on your computer so you can upload yourself.
I don't know how well the Web module is regarded, it seemed very easy to knock something together very quickly but a comment by Scott Kelby in a B&H made me wonder if it is just looked upon as a bit of a gimmick.
The Lightroom channel on Youtube has some great videos if you have some spare time.
http://www.youtube.com/user/AdobeLightroom
It of course also works with Photoshop and Elements so you can move files between them easily.
I suppose the question is, what do you use Photoshop to do?
EDIT: I found an article by theturninggate.net about that comment by Kelby which is quite interesting
http://theturninggate.net/2012/03/nobody-uses-the-web-module/.