Unless there have been significant improvements since I last had the pleasure of the pay lounges... I really wouldn't bother. I've been there for free a few times, and ended up leaving, as they had so little to offer.

If you're going to be spending most of your time in the Yotel, I'd personally go landslide and visit the supermarket in Schiphol Plaza, if you want to load up with things to take with you (bearing in mind that non-Schengen security is at the gate, so you don't need to dispose of liquids until boarding) - you'll get much better quality and value for money.