Rich,
Hand-pours are usually "softer" (more flexible) and can have unique color patterns/combinations that are difficult to achieve with injection-molded plastics.

Some people swear by them, other swear at them.  Many people like them due their uniqueness and (sometimes) realistic colors.  Their softness gives them added action with very minor movement on the angler's behalf - a bonus for very slow presentations.  However, because of the labor involved, they are often more expensive than injected plastics, and their extra-softness leaves them prone to tearing easily, making them rather expensive to use.

My experience has been mixed - it really depends on the source.  Hand-pour companies are often small operations, sometimes run out of somebody's garage.  So it really depends on the experience and ability of the person doing the work.  Colors, shapes, and quality vary greatly.

This is generally true, but not always.  For example the ZipperWorm company uses machines (robots) to "hand-pour" in mass quantities.  The Aaron's Magic worms are another example of machine-made "hand-pours".  Although still expensive, the quality is maintained batch-to-batch, and the colors can be very appealing to both anglers and bass.

This by all means is not an all-inclusive answer, so I encourage others to chime in.

I really prefer quality injected stuff over hand pours. Kalin, Yamamoto, Zoom, Luck E Strike and some others. Secret tip: Plastics weigh a LOT, don't overload your boat. I have some favorite colors, but really don't get too fussy over it. Green Pumpkin will pretty much catch fish, if there are fish to be caught. Natural colors rule.

C&R, Steve