The verdict: Heeding the warnings of commenters online, I added lots of cheese to the recipe, so it was tasty. But I didn't see the point of adding eggs to my mashed potatoes and baking it in a pie dish other than for pretty presentation.
The take away: Hiding greens in your mashed potatoes and cheese is a brilliant way to pack in more rich vitamins and minerals from seasonal leafy vegetables (or bagged spinach) without punishing your taste buds.
In the future, I plan to just make a version of mashed potatoes something like this: Saute spinach/kale/spinach/arugula/ romaine/whatever's in season with olive oil and minced garlic; cool and chop. Add greens to potatoes mashed with milk and a sharp cheese like parmesan or cheddar. Serve as a side dish.