Oh man hard mode is fun. Having all the weapons unlocked from the beginning seemed like an odd move but since the enemies are faster it seems mainly pointless to use the default weapon - I'm using the cluster bomb, slash claws and freeze shot (I forget the actual names) and I've not needed to use any other weapons. The freeze shot is brilliant for the stage enemies (fast paced, decent range, decent damage, freezes enemies so you have plenty of time to dash combo through them.
The faster pace was an eye opener on the first level, but I've gotten things down well now. However MN5's level have a couple of really annoying bits that seemed ill thought out (as does the very end of MN2's level) but otherwise I've had no issues clearing the levels (I've finished the main 8 bosses, just got the "fortress levels" left.
Boss fights are really fun as well - MN7's fight being my favourite of the bunch - its a really fast paced battle that requires precision, especially his multi slash attack which is really sped up compared to normal mode (but bizarrely, due to it being faster makes it easier to dodge!). Really the only annoying bosses I found were 2 and 6. 2 because if you mess up and get frozen you'll be taken loads of damage, 6 is probably just my least favourite boss battle personally. 3 isn't great if you use the weapon she's weak to, as the fight is over before its really began.
Definitely liking this the more I'm playing, I was enjoying the game to begin with but now I'm starting to love it. I still stand by the game being quite rough round the edges and has issues, but I don't think its a bad game by any stretch of the imagination.