I'm personally surprised because although we all know this sounds old, I honestly will not listen to Parallel Hearts by choice (usually I'll let it play out when I'm working with my hands or outside, and too preoccupied to just skip one song), but I like the sound of this sample.
Several past comments caught my attention that pertain to Hikaru: I agree that we shouldn't be surprised that it's a pseudo-FJ chorus progression, as Hikaru has been blessed with 66% of the recent leads (which she had done well, regardless of the song). However, I also remember that translated interview had Hikaru stating that there would be "emphasis on tonal changes".
Personally that makes me interested to hear Hikaru's vocals in this song. I don't know if this is a common thought or not, but in my opinion, Hikaru is the singer with the most noticeable power to move the aesthetic of a song with her tone alone. I hope it will give the song at least a hint of "inspiration"-sound (not regarding the song's mood, but rather some new kind of musical progression), because I agree that it sounds nostalgic but is potentially touching on generic.
I also agree that I'm tired of the recent abuse that the flute has been getting in Miss Kajiura's work. On the topic of traditional style, I'm interested as to the songs that would come out if Kajiura decided to have Kalafina or FJ collaborate with, say, the band Rin', had they not disbanded. (If you don't know Rin', their album Inland Sea is on Spotify and iTunes)