Unity
I was an Ubuntu convert until forced to upgrade Ubuntu 11.10. I don't normally ponder aesthetics too much, but Unity is pretty ugly, but more importantly, misses the mark and is not very intuitive. Surely development time would be far better spent providing a decent 'Windows Explorer' style file manager, program/drive installation methods - emphasising appearance over functionality will start the rot for Ubuntu distributioringns, I'm already considering other distros.
This is a comment on "Disable Unity on Ubuntu 11.04"