I would also add that LR is usually not very useful to:
a) artists and amateur photographers who have enough time on their hands to work on one photographic image at a time, spending considerable time either experimenting with it, or tweaking it to perfection;
b) graphics designers and others who tend to use the compositing, layers and vector graphics facilities in PS; or,
c) amateurs who take the shotgun approach to photography and post practically everything they shoot to Picasa or some other photo sharing site and aren't at all interested in rating their photos, keywording them, generating (on the fly) different subsets, or even just different sizes and crops for different end uses or different groups of viewers, generally establishing an efficient workflow, etc.
OTOH, LR is an incredibly useful tool for working event, sports, portrait, and product photographers (ie, paid pros) who need to quickly select the best images from the hundreds or thousands they shot in one afternoon, who need to get a set of very good (but not "perfect") professional quality images out the door ASAP, who may need to look up one particular image out of the 50k images that took in the past year, who repeatedly need to show their work to art directors and others, who often need to quickly throw together a photo book, etc.
The above distinctions probably best captures the intended audience for LR.
Tom M
