One question to all

Its her voice I think. Or that what go's for me. It this unique sound that just......Its Magic!

Other than the obvious, for example her attractive character design and voice characteristics, I 'm looking forward to hearing what music creators think of her.
Anybody making music with Hatsune Miku here?

Pehaps one of the millions of reasons is that she's one of the Pioneers of Vocaloid. Second, who couldn't love a character of the simplest design with the most excellent magic? XD

Plus, her lovely voice made known to each and every otaku alike, for one cannot call himself an otaku without hearing Miku's voice.

Probably because she's one of the earlier Vocaloids, therefore making her more well-known, but also:
- she's young
- she's feminine/girly-cute (whereas Luka is more cool/masculine, despite her figure...)
- twintails!
- she's small and adorable, thus making the otaku masses want to protect her? that's a very strong feeling that exists around moe-charas...

"Hatsu" means one/first

Do not question, just accept it. You can't fight the truth. Seriously, though, Character design is probably a major factor in her popularity. by giving it/her a visual appearance and personality, it helps people to relate and accept, so that's probably one reason. That, and people love music.

She came first, therefore people associate Vocaloid with her more than any other.
Plus she was thoroughly promoted as well :3

I think also because she is that type anime girl.
Long Pig Tails, School like sailor outfit, short skirt, high-thigh socks, hair colour unnatural, petite, and cute voice all in one. kinda like a symbol/icon in a way.

Btw isnt she the first born, (exception of LOLA)?

Miku is the first of Vocaloid2 only, I think (there were definitely other Vocaloids before her, English and Japanese).

Hmm...I'd say she's so popular because of her design, it's just...aesthetic XD Zettai Ryouiki and pigtails (and also DFC in some cases like Project Diva and fanartists).
Her (default-ish) personality is also a little bit tomboyish, so she's kinda fun XD

Miku's my favorite (though she definitely fights with Rin and Len sometimes) but I think the idea of the Vocaloid in general is pretty awesome. Especially with the fact that they all sound so amazing...

Its her appearance. Everything about her and her appearance is special.

She's a virtual idol.
She gives you power to dictate her songs.
Her hair color is rather special. Special enough for me to call it Miku green, when I'm doing her ita-plane.
Her painted fingernails too.
Her costume. Its grey. With those sound symbols woven into her skirt. She wears a TIE too, instead of a standard BOW.
The signature twin long ponytails. The hairclips. Just awesome.

OK, enough. *scampers off to hug MIKU DD*

Clever Marketing. Meiko and Kaito failed to capture the masses, so Crypton had to kick it up a notch. Create a simple, but recognizable character with as much appeal as possible. Then do cross promotion with other companies. The rest is history. (the way I see it anyway)

I love her design; I have a thing for limited palette characters (like Rider). I'm not into her music all that much (super high pitch gets irritating sometimes) but I think she's really cute.

I like Rin and Len the most. ;___;

Guess it's just her character design that wins most people's hearts. I personally don't really like her voice. Miku Append is a different story though...

As many say she has a moe factor already, next she is a virtual idol, but as she is considered first (of the Vocaloid2 series) she was promoted the most. On another note, because people are allowed to create any style of music with her, you get many forms of Mikus which add to her popularity. Example the song Moon, gave rise to her popular design of VNO2. And other things are also associated with her: leeks = Ievan Polka, and that Hachune face.

I like the character design overall -twin tail hair style is my poison. However, I don't really like her songs compared to Luka's.

Beyond just character design, i thnk i big factor is that since miku was the first of that generation of vocaloid to come out means the first hit songs made buy the most highly skilled composers (read, RYO) were all done with Miku. creating an initial surge of popularity, which held momentum as other vocaloids were released.

As a rule, popularity begets popularity. "Top downloads" will always be top downloads, because they are at already the top of the list. New, and potentially better, downloads that are much farther down the lists can have a hard time attracting attention in the first place. Many people don't bother to look for diamonds in the rough.

In my opinion, she has a cool character design. That was my impression when I first saw her, but didn't know what she was from. She has the most popular songs, and she has the most energetic voice. I feel like pumping my fists listening to Miku. Luka is my 2nd favorite because I like some of her songs like Double Lariat. However Luka is more somber in voice. That's just her style.