I did almost a year's worth of credit through CLEP tests and I loved it!  To pass a CLEP test (or similar test like DANTES/DSST, ECE, or TECEP), you either have to know the material already or else learn it ahead of time through independent study or some other means.  Either way if you pass the test it demonstrates that you know the material, so I don't really see a different between that and taking a class to demonstrate the same thing.  That's not to say I think they're right for everyone in every subject, but for those who can pass them, I don't see a reason not to do so.

-=Steve=-