I haven't yet figured out the best way to share an image library between different computers.
According to Adobe's Lightroom FAQ:
"Will my Lightroom Library synchronize with different computers and networks, or am I limited to one only?
"Lightroom shares a limited amount of information using metadata stored in XMP format. Lightroom plans to add more robust support for multiple computer environments in future versions."
I am pretty impressed how well Lightroom accommodates my existingworkflow and organization including storage locations and file naming schemes. My image file organization system divides original and derivative files into two major storage branches. It's clear that under the Lightroom model (and the Bridge/ACR system for that matter) that organization may need some adjustment. Or, at least, I will need to think about the term "original" differently since changes are constantly added to the XMP data accompanying "original" files.
As I noted, Lightroom is quite adept at dealing with files that are located on a server or other computer, and it can deal with files coming and going gracefully. But it's not really designed to support multiple computers or users working on the same file (never mind the obviously complex problems of simultaneous access). It stores your net Lightroom adjustments in the XMP data for the file (either in a sidecar file for RAW or in the metadata of the file itself for JPEG and DNG). There is a preference to always write XMP data to the image files or it can be done manually through a menu. But that data seems to be a single snapshot. Your adjustment history, for example, seems stored in the Lightroom library on your computer.
There may be a roll for Windows' offline files/sync center feature. But I tread carefully.