First time I heard, only a minor impression was there, improving over subsequent times and now it has kind of got into my head. These days I’m listening to Delhi 6 more than ‘often’, that is atleast a hundred times from start of day to the end!
AR Rehman’s music is just as captivating as it always is. There are very few ARR songs that are not in my list 
Dil gira, is easily the top most on my list, ‘cos I kind of feel it is the song sung by a soul. Next comes rehna tu, sung by ARR himself. Its a marvelous song, his voice blending smoothly with the music.
Masakali comes a decent third, ofcourse the song has been hugely popular..
but you know… Noor recited by Amitabh is also wonderful.
Others are so so, kaala kaala bandhar peppy, not sure if would be projected, Genda phool is folk, Bhor bhaye is classical, thumre bhavan me, arziyaan saare are devotional types… If Rayakesh comes up perfect picturization, even the so so songs could turn out to be completely different. Listen Here
Now I just have to wait for the movie
Abishek, Sonam and Rayakesh
Updated:
Search for dil gira, led me here, nice read.
http://chinmayisripada.blogspot.com/2009/01/delhi-6-dil-gira-dafatan.html
