Sudoku 10'000 can analyze every puzzle and rate it on a scale from 1.0 to 10.0.
It will also list all the required solving techniques.
BYOP (bring your own puzzle)
Synchronize your puzzles and settings across multiple devices and keep your progress if you get a new device.
There's nothing you can't configure, from input methods, to level of assistance, the appearance of the board, colors and fonts and much more.