Marc,
I've always drip acclimated my inverts and fish...corals I've really just temperature acclimated by floating the bag and then added them directly into the tank. I've not lost any animals due to acclimation. I usually go a little longer on the drip for shrimp and starfish, etc. than for fish (2-3 hrs) vs. (1-1.5 hrs).
These have been my experiences. Obviously, there is more than one way to do anything and many people have great luck with the "float the bag and add water" method. I just feel the drip gives me more control to do it slower and exactly add a little water at a time.
Regarding your shrimp losses...I don't know that anyone could say for sure what caused it. However, if the acclimation was slow enough even shrimp should be able to adapt to completely different water parameters.
Matt