Assuming you get one that focuses consistently then this lens is hard to beat at the price. It's the perfect introduction into prime lenses for those that never tried them.
The biggest issues with this lens are its relatively slow and noisy focusing motor, and the fact that if you have a more modern body that can do high fps, this lens will restrict it to 3.5fps when using AI Servo mode (I'm told it's something to do with the very old design of the lens). This last issue alone makes me want to buy another 50mm prime.
But really, for $125 brand new it's hard to complain!