I suppose I'm one of the few people to live under a rock these days. My only connections to the Vocaloid fandom are this site and the songs posted to Youtube. My biggest problem with the western community in particular is a lack of Vocaloid metal and hard rock being made compared with how much the Japanese community makes. Aside from that, most of my criticisms of the western community also apply to the Japanese community.
The western community is exactly what I would expect it to be given the circumstances. The public perception is that Vocaloid is Japanese, and Japanese media is stigmatized in the west. On top of that, westerners are often skeptical of machines doing the work of humans, and often frown upon technological help in singing. Vocaloid strikes many, if not most westerners as strange, pointless, and unattractive. As a result, Vocaloid is very niche in the west despite our best efforts, which brings me to another problem I have with the western community in particular:
I believe most western Vocaloid fans reject western Vocaloid designs that are not typically manga-styled and cute/pretty. I want western Vocaloids with just plain cool designs, too. I think it would help Vocaloid enter the mainstream here. We already have several western Vocaloids that don't have Japanese-influenced designs, like the Cyber singers, Chris, and Amy, but they are very unpopular.
So there's my rant against the western Vocaloid community. I still like it a lot, though.