It generally should be safe because Dell refurbishes the laptops themselves and includes the standard 1 year warranty. Desktops and laptops sold on Dell outlet does not always mean that the laptop has failed and Dell fixed it up. The outlet also sells PCs and laptops that the customer returned for whatever reason. Maybe he/she didn't like the color.
I have no experience with Dell. I have only purchased laptops from IBM (back in 2003) and Lenovo (last month).