Here have been a couple of weird experiences I've had with a Ubuntu LiveCD or LiveUSB:
1) I had one of the original Chromebooks (CR-48). I ended up wiping ChromeOS and installing only Ubuntu 12.04.0 just after it came out. It worked like a charm. About a year later, I broke something and reinstalled Ubuntu using 12.04.3 on a LiveUSB. The LiveUSB worked perfectly - screen resolution, wifi, trackpad all worked fine. I installed it (once installing updates, once stock from the USB drive) and both times screen resolution, wifi, and trackpad all broke.
I ended up downloading 12.04.0 and installing it then upgrading to 12.04.3 after the fact and everything worked perfectly once again.
2) I purchased a Toshiba Portege z935 and the LiveUSB worked perfectly, namely the wifi. After install, wifi was extremely slow and basically couldn't load any pages. The answer was that Bluetooth conflicted somehow with wifi and Bluetooth had to be disabled to get wifi to work. Yet both could be enabled in the LiveUSB version, no problem.
So my question is, why does this happen? Why does everything work perfectly from the LiveUSB version but then get broken when installed on the system? Is there a different way to install Ubuntu that would allow things to be installed over exactly as they were on the LiveUSB version (drivers, settings, etc)? Are there assumptions that the install makes that I could override somehow?