I like them. They help. The players can just look at their mutation/artifact card to see what it does. When it comes to artifacts I can easily sort out the ones that I don't want the players to find yet and use the rest as a deck to draw random artifacts from. Sure you can use tables and charts and the players can look in the rulebook for the mutation effects, but the cards makes the game more smooth to play. The same can be said about the markers. Of course they are not needed. You can write down how much grub, water, ammo and mutation points you have, but to just take a marker helps with the bookkeeping.
“Thanks for noticin' me.” - Eeyore