The heating element that creates the warm air is probably defective - a fan blows air across it - your blown air is cold.
As for your opening question - "is it worth repairing?" I am unable to answer - how long have you had it? How much will a repair cost? How much will a replacement cost? How much can you reasonably afford? are all questions you need to ask yourself.
Good luck...
Peccavi
May 2009
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