Mechanic Q: Is it ok to install an after market alternator??

I have a 04 G35 in need of a new alternator. After market is about $200 cheaper...but will it last?

Mechanic Q: Is an after market alternator reliable??

I have a 04' G35 in need of an alternator. The after market alternator is about $200 cheaper than the dealerships. Is it ok to install the after market product and will it last?