Reese's pieces are like M&M's but they have fewer colors and the chocolate is swapped out for peanut butter. That way you can argue that they have protein so they're healthy.
I think they taste really good, especially since they melat in your mouth. They are practically perfect except that the candy shell can be a little too sweet and sometimes it makes my teeth hurt. If you've ever tasted Reese's peanut butter, you know that it's like regular peanut butter but with an extra cup of sugar, which is actually kind of perfect for a candy. However, you don't really need the sweet peanut butter and the sweet candy shell together. It's a bit of overkill.
My main problem with these though is that they're addictive. The bags seem small, so before you know it you have eaten the whole thing. Plus, one problem with subbing the chocolate out for peanut butter is it adds more fat and calories.
But, just like anything else, these are great in moderation.