Thinking about this, I do think 'live view' is mostly useful for tripod work as Old Clicker said and sometimes in awkward situation where you might need to hold it over your head or something. Then only a flip out screen would work.
A dslr is going to be much heavier than a p&s especially when you start using the larger zooms or primes.. I think anything 150 and above would be too heavy to hold steady unless braced as you would be by using the viewfinder.