If a game is properly prepared in regards to FULL sanding, it is a good alternative if NOS or reproduction playfields are unavailable.
If this step is skipped (or partially sanded) you will not be a happy camper in the end.
This is not the same as some cabinet artwork for example, that some can "cheat" and hide the short stepping (including painting the cabinet black OVER the original artwork).
Many times the inserts need to be "reset" for proper leveling, and need reglued, or outright replaced.
Overall the process will take roughly half the time of doing a full playfield swap if an owner is experienced.
Some do use clear coating afterwards, but make sure the overlay adhesive is really solid, or you waste a lot of time and money down the road if it lifts just like D1M.

Scrutinize the overlay image of the manufacturer to look for printing "blurriness", as they is a sign that the production ink either bled, used an improper transfer process, or cheap materials.