Let's hope the bugs aren't as bad as those from 5pb. Otherwise it would defeat the purpose of having all modes available out of the box without need for DLC.
Here's the current bug report list. Taken from cave-stg's forums:
-High score on the top of the screen doesn't always update when you surpass it.
-High score doesn't update properly when you use the extra small side screens on the wallpaper.
-Replays don't play back normally
-Strange slowdown at the start of stage 2 (I'm assuming he's talking about Arcade or 360 mode here)
-Some sound effects get really quiet randomly
-The tutorial bug works in Arcade mode. Doesn't seem to work in 360 mode, though.
-In training mode if you set "stage default" to the power level for Stage 4, it starts you off at MAX power, which is higher than it should be.