I know this isn't a direct answer to your question, but...
Any testing, regardless of what type, is insufficient by itself. Unit testing/code coverage is for developers. QA still needs to test the system as a whole. Business users still need to test the system as a whole as well.
The converse, QA tests the code completely, so developers shouldn't test is equally as bad. Testing is complimentary and different tests provide different things. Each test type can miss things that another might find.
Just like the rest of development, don't take shortcuts with testing, it'll only let bugs through.
