I would hardly call Bridge/ACR integrated into PS. More like a thrown in RAW converter, a very good one mind you, and a file manager replacement, with a few bells and whistles for imaging folks. There is though absolutely no integration.
I see that Bridge can do collections and smart collections, but as it seems that all of the images have to be in one folder it is not really very helpful, unless I want to stick all of my images in one folder that is. In LR I can have images from multiple folders, in either standard or smart collections. I also have the option of displaying all of the images that are in the library at once. Or if in a folder, all the images in any subfolders. Also although only just introduced with the latest Beta version, I can now work on images that are on removable drives, or unconnected network locations. In the older versions although I could not work on the images I could still see them when disconnected. Bridge cannot do that, and there is no getting around it at all. As well as the management and processing modules there is also the very good print module, much better IMO than the printing options available in PS, as well as the Slideshow and Web modules, which beat the tools available from within PS hands down for usability/customisation.
LR is truly integrated into one logical whole, with a consistent interface and tools. I do not see Bridge opening a file directly to the Crop tool in ACR with a single key press, or to the PS printing tools. For the things photographers do with the most regularity LR has Bridge beat by a long margin. Finally with LR4 Adobe seem to have a product that for most photographers will do all the PP required for between 90 and 98% of their images. LR5 looks in improve on that ratio. Yes there are things that you need an external editor for, but fortunately Adobe do not force you to use only their editor, you can pick one to suit your needs.
As a user of the full CS3 suite, along with PS CS5 and LR4 Bridge is still very useful to me when dealing with file types not supported by LR. In situations where I have done the photography for a site, as well as the coding I will do all the image editing in LR/PS then once I have finished product ready I export the JPEG's to the hard drive that I use for those projects, when I then use Bridge to manage ALL of the files needed.
Alan