The value of an additional LCD view depends entirely on the sort of
photographic work you're doing. For close-up shots of complicated,
highly reflective objects a live view facility with pinpoint focussing
is a real boon - as is the ability to see the image in real time on a
computer screen. It allows for some very specialised techniques,
such as manipulating the depth-of-field by the millimetre.
In fact because of the limitations of DSLR live view at the current
time I'd say it was more of a function of use to the studio
professional than the amateur.

The Canon 5D II (and possibly other cameras) lets you connect to an HD
display so you can get an even bigger live view. I haven't tried this yet.