Big Bang Sudoku is a decent sudoku game, but nothing more. The one feature that seems to set this game aside from other of the plethora of sudoku apps (iTunes link) is that it includes 10,000 different pre-generated sudoku games.
The options are kept to a minimum - there are not options for auto-fill pencil marks, or fill in all obvious spaces. You can manually enter the numbers or pencil marks with the game optionally showing you which numbers are wrong.
As far as the Sudoku goes, this game works. It's easy to fill in the squares, and the games seem properly puzzling for their respective levels. Though I'm no sudoku expert.
The graphics are all well done. Animations are used well where they are used. And there's a nice fireworks display when you complete a board.
Oddly, Freeverse also offers a free Sudoku game, FreeBee Sudoku (iTunes link), which seems to be the exact same game, but ad supported. The only difference is they removed the genie and inserted a bee. Odd that they wouldn't just offer an ad-supported version with this name instead.
So, I while this game is very well made, I can't really recommend it. Mainly because I'm cheap. The price is too high and it really offers nothing that other games do not -- other than a really nice UI. I'd suggest trying FreeBee Sudoku (iTunes link) to see if you like it instead. If so, perhaps this, paid version would be an option if the ads get annoying.