Finished! (Three times).
Good: Everything. Always wanted a game like this, a DSS with many modes, difficulties, a + mode, full GameCenter, RadianGames own upgrading system behind it, and with a huge maze feel with lots of different enemies, explosions and bosses. And all the RadianGames good things: music, controls, polish,...
Bad: Lacks a story mode that would have made it even more awesome.
Conclusion: RadianGames always delivers, and Inferno+ is their best game yet (with permission of Super Crossfire). Games like these are rare on the AppStore, a true gem.
Final Rating: 5 out of 5. Must Have.