Okay, so, um... starting with Qazi (LOL)... I think his improvement is beyond what anyone expected. Before I think he was saved because of his personality - now I can safely say that he deserves to be saved. He sings really well these days... I can't believe how much he's improved. I think it's also very evident that he's paying a lot of attention to his singing - it's not all about the dancing anymore. Yes, there's a natural-born talent of dancing in him which means that he can dance better than the other contestants without trying at all, but before you could see that he put a lot into his dancing/performance. Now he's concentrating on his singing. His dancing/performance, though still good, isn't as good as it used to be. It's still fine, though, because I believe he has it in him still and he can bring it out whenever necessary.
Mona. Yes, she's out of Gurukul, but still. She has evolved a lot - as all the judges have said, she was enclosed in a little shell, but she's out of it now. I'm really happy for her. She has a great voice, and now she's starting to open up.
Arijit... his singing is really good, but lately he's been working on his performance too - his dancing skills, aadayein, everything is going up.
I think those are the only contestants who've shown any significant improvement... I might add some later, but for now, let me hear what you have to say.