Definitely, you should upgrade your Dell mini from 10.04 LTS to 12.04 LTS, it works okay!
My experience in upgrade process from 10.04 to 12.04 was not smooth, I was using alternate 12.04 iso image to upgrade (offline upgrade), but because my Dell mini was also installed with packages from various PPAs (particularly GIS stuff), the upgrade process was refused to continue with specific error message saying that the upgrade can not calculate the size of packages to upgrade, something like that.
So, I take a short cut, make a clean install (yes! using the same alternate iso which burned to bootable usb). And it works!
I am happy 12.04 user now, and everything works, like wireless, sound, bluetooth, video cam etc, even Rythmbox works better compared to when run in 10.04.
And for sure power management in 12.04 is flawless, like: when you're running out of battery power, the system will to refuse to activate when you push power button, until you connected to AC power, but you're not losing your previous work, because the system is not actually shutdown! it just like a normal system suspend in action.
And I should say, I love Unity...
On performance side, I can log in using Ubuntu 3D but the Intel Atom processor seems to work better when I log in using Ubuntu 2D, which I don't mind at all.
hope this help!