RUBAIYAT  Seemed to produce an error where I couldn't get a 2 but needed one.

Don't know if I like the select from numbers pop up, at least I should be able to chose this or not.

Layout is simpler than some others but not really that aesthetic. Things that throw me are the grid is not square and I don't like the fat serif font used.

After I closed the puzzle that had the error in it, the only choice I had was to quit the application, all except Open Recent was greyed out and the submenu off that was greyed out.

Definitely has room to grow.  
(Version 1.0.2)

RUBAIYAT  I guess this is just early days but it crashed on me 2 steps into playing a puzzle. It also generated a puzzle with an obvious error, a 3 inline with an open box which could only have a 3 in it.

Overall it is very unattractive. It needs to be tidied up and simplified.

Use some white space, don't crowd things and offer contrast in line thickness and characters.

Needs to make viewing selections straight forward as well.

It is not like there are that many options to Sudoku:

View : w/wo hints, w/wo eliminations, color of answers, font, number of squares, background

Difficulty: Easy, Medium, Hard, Einstein

Feedback: Show errors/Don't show  
(Version 1.0.2)