Nice to see interest in this here. Program slicing can also be used for everyday tools too, not just formal verification. I did some research with Microsoft Research trying to show how it can be used to discover which parts of program will be affected, before you make a database schema change. I think program slicing has a lot of potential, and is generally under-appreciated because a lot of the research looks for conservative and safe (i.e. no false positives or negatives) analysis. When you relax this constraint, there are many useful things you can do with slicing.
Details on one such example here if anyone is interested: http://www0.cs.ucl.ac.uk/staff/w.emmerich/publications/ICSE2...