For the most part, yes, it's safe. However, it's not always the best value. I would only buy from a big distributer (like Amazon) and have a good look at the online reviews, especially for reviews that were made several months after the purchase (as opposed to directly after). A lot of the cheap generic batteries don't last very long - both in their initial charge, and the amount of charges they can handle in a lifetime.
I've bought several generics for past cameras and had mixed luck. Some worked great, others die out quickly, most were somewhere in between.
My take is: they work find for point and shoots (if you get decent generics), but I don't care for them for my SLRs. They work ok for a little shooting here or there, but if I'm going to use it professionally for several hours it's just not worth the hassle of dragging along extra batteries that I don't trust. Some feel the same way about using them for travel, others find it doesn't bother them and saves them some money.
