It's relatively safe (always check the seller's ratings and read the fine print – also, Apple warranties are locked in their system to their products, so unlike some companies they tend to honour that even if you didn't buy from a retailer), but it's still one of the less safe places you could try online by comparison to other common suspects.
And for the new MacBook Pro with relatively high demand, I'd be surprised if you saved very much at this time. The small difference could be worth avoiding the small points of uncertainty.