I find that logging is much less necessary since I've started using TDD. It makes it much easier to determine where bugs lie. However, I find that logging statements can help understand what's going on in code. Sure, debuggers help give you a low-level idea of what's happening. But I find it easier when I can match a line of output to a line of code if I want to get a high level view of what's happening..
However, one thing that I should add is this: make sure your log statements include the module that the log statement is in! I can't count the number of times I've had to go back through and find where a log statement actually lies.
