Erik, you could not be more correct!
Folks, DO NOT attempt this unless your LR images are completely backed up and safe. It is not even a good idea and I have learned the HARD WAY.
Thankfully my images are backed up. Going forward will be using C1 because the way it renders Canon files is strikingly good. They have certainly done their homework here and it shows in the RAWs. Gorgeous
However your images that were in LR w/adjustments stand a very good chance of being messes or worse, totally corrupted. Sadly, running them back through LR is of no use, they are burned. Be very careful. Some come over just fine and some are destroyed and some are not destroyed, but useless nonetheless
Don't expect to much. The processing engines are very different.
Simple adjustment may work. The PV 2012 that was introduced with LR4 does a lot of tone mapping on highlights and shadows that seems to me to much different from C1, I don't think that converts well.