It's not what ya might think. My iPod touch 4G was untethered with Corona, and it was very smooth, BUT, I found through some digging and trial and error thy corona (the latest version ) will disable ALL installed Daemons. The Daemons that are installed from Cydia.
More specifically, licensing daemons.
For example. If you apply Corona.,...and the install IntelliScreenX, you will not be able to use ISX because Corona will disable it's activation daemon.
And it will do this with all installed daemons.
However, if a 3rd party daemon is already installed before installing Corona, then it will remain functional.
If you already have your phone setup and have everything installed that you want installed, Corona will not be so bad.
But if you restored, and want o tether jailbreak, then install Corona...................you are in for a hell of a time setting up you phone, and you'll probably end ripping your hair out, being so frustrated, that you canny make anything work, and are encountering one problem after another.
My end conclusion:
AVOID CORONA AT ALL COSTS. JUST APPLY REDSN0W BETA 3.
Didn't realize redsn0w was updated 3 times and Corona was only updated twice?
I don't know if that has anything to do with it but Corona needs to be removed from Cydia. This is for sure.