It tasted even better to me after a day or two of letting the flavors soak in and mingle in the refrigerator. And no problems with wilting; everything keeps nicely.
Substitutions (suggested by the friend who passed on the recipe):
-Spinach instead of arugula
-Red wine vinegar instead of sherry vinegar
-I chose Pink Lady apples, and loved the tart-sweet flavor
Also, I wanted to use Parrano cheese instead of Gouda, but didn't find any at the store
For the quinoa, I used organic tri-color from Trader Joe's, and cooked it in the rice cooker instead of on the stovetop.
I set aside a small amount of salad without the balsamic vinegar red onions or red wine vinegar (for those with dietary restrictions prohibiting alcohol), and I actually ended up really liking that version, too. It's less tangy without the vinegar, so it's a milder combo of veggie flavors, olive oil, salt and pepper. If I were short on time, I might make that one, since it would cut the step of cooking the red onions.
Bonus - my 6-year-old even ate some as a side for her dinner.