I wouldn’t call Tinderbox, iMindmap or Xmind ugly but I don’t know if not being free rules them out. If you go to the browser-based (and therefore cross-platform) ones, bubbl.us is free, simple and attractive, and it lets you cross attach nodes.

I agree that this is one of the most sorely-missed features of mind mapping software, because their designers mostly worship tree hierarchy a la Buzzan. You need to go to concept map software for freedom to connect anywhere to anywhere.

Vic
The master list of mind mapping &
information management software