One really good addition was coins actually being used for something other than replenishing health (and at times being required to get certain stars). Since you lose all your coins when you die, it makes some parts much harder. And, I like the addition of automatically keeping Time attack records for every star, and the fact the clock becomes disabled in Speed run challenges when the star appears, unlike Ghostly Galaxy's purple coin challenge that was annoying because the timer kept going after you got all the needed coins.
Only three times the Cosmic Guide appeared for me during the first 120 stars: the Slide in Tall Trunk Galaxy, the Rock Mario level in Melty Monster Galaxy, and the Cosmic Clone star in Flip-Out Galaxy.
But what is really good about this is that I felt encouraged to play every level, unlike the original that has its "oh not this again" moments. The Purple Coin challenges felt properly done this time, other than just throwaway stars to fill up the usual 120.