It's definitely past its prime in terms of popularity, though it's far from dead. I think it will always get some use, but its glory days are gone.
I don't much care for it, even though I have a cousin I love named Jennifer. It's just so generic-white-girl (my cousin isn't white of course) and the fer ending isn't very atractive. I think Jenny is cute, but I really don't like Jen. If made to pick a jen name I'd choose Jenna without a second thought.
Before you criticize a man, walk a mile in his shoes. That way, when you criticize him, you're a mile away and you have his shoes!
Steve Martin