I would definitely like to make a few comments though, if you don't mind.
Nihira was one of the best of the best singers in this challenge. Initially, she had trouble with putting emotions in songs, but she developed that as the challenge came along. Imagine how many hearts were pierced when her final song "rahe na rahe hum" sung. The fact that no music in the background was there, her voice, and the shock to everyone that she got eliminated all made that one a haunting experience.
I do agree that Himani did sound monotonous at times. I don't know if monotonous would be the right word, but sometimes, there were issues with her voice dynamics, especially in the songs of the lower register, like the "jiya dhadak dhadak" song.
Hemachandra was the best! Ami ki bolbo? Since his name came up, I would like to argue one case about him.
I think that messing up on Bachna Ae Haseeno was something completely ridiculous. The tracks were made in advance and you'd literally have to memorize the song. This means beyond the subtle nuances and the lyrics, you had to memorize exactly how many asthayis, antaras, etc. had to sing. I understand that many tracks today are prepared when playback singing, but I am almost certain that live concert shows will have good musicians to help them out.
Vinit has extreme potential, although he did have a good deal of breath control problems when performing. I'm sure with proper guidance from a bona fide guru, he will be able to overcome that (as well as the fact that he is now branded as a Sonu Nigam clone). He'll be one of the best singers if he puts his own mind to it, and not HR putting things in his mind.
Debojit was the one who showed the most amount of improvement. He handles light songs pretty well, although we haven't heard a great deal of his fast songs. He does sing Kishore Kumar songs well, although I must say that he doesn't have that strength in his voice to do a Kishore-da song from the mid-70s onwards. Kishoredas voice was a unique one as his voice started sounding more thicker from 1976. FYI Kishore fans: Kishoreda's voice sounded the thickest in his duet w/ Lataji "husn ke wadiyon mein" from Waaris (1988).
Once again, thanks for posting the analysis!