If you own, use, and are happy with Photoshop, Camera Raw, Bridge, iViewMediaPro, a slide show program, a simple web gallery generator, and a printing RIP, then – no, you likely don't need Lightroom.
I do have all those programs and am quite happy with them, but I thought I would see what all the noise about Lightroom was about, so I dug in. First, let me say that your DVD with Jeff Shewe "Adobe® Lightroom™ beta 3 Tutorial" was very helpful at answering my questions, and a true bargin at $15US. Even though beta 4 is available now, everything on your DVD is still current.
Adobe's website also has some excellent information. The podcasts on Lightroom Beta were particularly helpful: feed://rss.adobe.com/www/special/light_room.rss
After listening, reading and using the program some, here are my initial conclusions:
I think Lightroom will replace Bridge and Capture RAW for me.
Photoshop will still be required for working on selected parts of an image (local corrections) but for adjustments that affect the entire image (global corrections) I see the vast majority of that occurring in Lightroom.
What is not clear is if it will make iView MediaPro unnecessary for me. It has always been a bit of a pain to use and having DAM functions built into Lightroom is certainly a plus.
• Better Grayscale Conversion
• Much nicer interface. It makes Photoshop and Bridge seem old-fashioned.
• Native on my Intel-based Mac (Bridge and PS won’t be until Spring)
• Excellent Metadata editing
• Tailored to deal with large volume of images
• It is database driven, not cache driven like Bridge
• It encourages a more efficient workflow that is not based on image-by-image adjustments
• Develop has some advances over ACR: easier to use curves, auto-grayscale, HSL, Split toning & Vibrance.
• Not pixel based, hence only global adjustments, no local corrections.
• Only deals with images, as opposed to all CS2 files like Bridge which can handle Illustrator, PDF and InDesign files.
• Currently Camera RAW can’t read Lightroom edits, but it will when the 1.0 version ships.