Posting for new page and more thoughts.
I couldn't wait so I bought MUSYNC.
As kassatsu stated it's a DJMax (Portable) clone and in that vein the aesthetic presentation is on the ball, lots of neon, flashy lights and led effects.
Two difficulties: Easy and Hard and options for 4 keys or 5 keys. In game the L and R buttons are used to speed up or slow down the notes respectively.
The timing is much less lenient than Cytus Lambda and (as you'd expect) is closer to DJMax.
No touch interface as far as I can tell, only the Vita controls (using O to confirm).
In 5 Key mode the middle key corresponds to either the Right direction button or the Square button.
Backgrounds are static, but graphical effects may alter the look during a song. There are small animations upon pressing the correct button on the corresponding key.
There is no fail-state and lowest rank seems to be C with sync of 0%.
Pressing buttons when there is no corresponding key doesn't seem to count against anything.
The results screen is made up of your Accuracy Ratio (Exact (Either 100% or EX), Great, Right, Miss), Sequential Ratio (Combo, Combo %), ADD.RAT (Your EX count and EX %), SYN.RAT (Sync Ratio) and letter rank.
Sync graph correction: Corresponds to letter rank.
Game only remembers your SYN.RAT (Sync Ratio) and letter rank for each song (and subsequently each mode and difficulty).
Pause screen has options for Resume, Restart, Quit.
No other option menu.
Song list seems to be made up of instrumental tracks and Chinese vocaloid songs (Makes sense, the developers look like they're from China).
7 dollars for this or 20 dollars for PSP version is all I need to know. TELL ME.
It's a DJMax clone, with clone being the operative word. Might be better down the line when they add more songs, but the PSP DJMax games are still content rich as far as games go.