I have two issues with Ubuntu 12.04 (upgraded from 11.04, 11.10) on my ASUS K52De laptop.
First issue: Booting fails, if it follows a suspension, then a wake-up and finally a shut down. If I realize this sequence, then, during the boot I see the Asus logo and after that I see only a blinking cursor instead of grub2. Then I have to recover grub2.
Second issue: Sometimes, my laptop doesn't shut down. It freezes on the Ubuntu logo and I must turn it down with power buttom.