The header is to big. If you used the [SIGPIC][/SIGPIC]-option vBulletin offered, you lose your picture during migration (too late for this forum, but maybe InnoGames could warn players on other markets). And I've seen on another market (.ch) that HTML does not work anymore. The biggest probleme with the new forum software is, that old thread links don't work anymore, which means, that many answers in help-forums or sent links to information in the forum are now useless.
In addition to that, I dislike the Like features in any means (twitter, facebook, forum).