I'll actually start with the objective qualities, mostly its downsides. For starters, this game is more or less completely obsolete. Compared to literally any other entry in the series, 2nd and Extend don't stand a shot. The songs are also old and if you're invested in Hatsune Miku or vocaloid in general, you probably won't really hear any newer favourites. The mechanics just aren't up to snuff and it'll be more tedious than it is pleasant. This is not a game I really recommend to anyone for starting out, or period.

However.

I'm speaking purely from personal bias. This was my first project diva game. Hell, it was the first rhythm game that I took seriously. I was utterly entranced by it, the game's art style fills me with an incredible extent of nostalgia. It's got a very crunchy look, and the music accompanying it fills me with nostalgia, for something I didn't experience as a kid. I wasn't a vocaloid kid, but this game just made me feel so cozy and warm playing it. This game holds an incredibly special place in my heart for introducing me to Project Diva, Hatsune Miku, and rhythm games period.