Dell and makers must warn you from this as the past history of battery fires and more means they can never tell you it's OK. Even I won't tell you that. You buy and accept all risk on these things.
That said, I just replace them from what's on Amazon.
I need to replace the battery on my Dell laptop. The Dell replacement is $139, but I can get one through Safe Battery.com or Amazon for a lot, lot cheaper. Has anyone had good (or bad) experiences with these off-brand batteries?