Damn game can be brutal period. I love it. Comets everywhere, really mean aux challenges and stars. Good show. I've noticed how ridiculously tuned some of the timed stuff and general challenges can be, very happy to see that being done. Usually way too much leeway in games for stuff like that.
You really didn't get much after you in the original Galaxy beyond comets, and this really ramps that up a bit. You can still kinda stroll through the main stars pretty easily, bout the Mario standard, but going off the road much can frustrate, in the good way!
Difficulty is gonna be person to person, but as someone who thrives on good challenge in games, playing everything on max difficulty, can steamroll most of what GAF whines about (Demons Souls, etc) It's givin' me a run for my money on a fair few things.
Though, again, I've only just beaten World 1. This is only my initial impression.
I felt exactly the same way for the first bit. The initial stuff is way more of a simple remix, but it'll heat up, don't sweat it.