Also, I read somewhere that launching at a conference means that you're one of dozens of launches over a short period of time, and you have to compete even hard

Also, I read somewhere that launching at a conference means that you're one of dozens of launches over a short period of time, and you have to compete even harder for coverage from press/bloggers. Whereas, if you launch on a non-descript day, you may be the only interesting thing happening all day, and get a copious amount of coveage.