PhotoKhan: What a low blow, disrespectful move by Adobe...
I mastered the previous versions well enough as to make an expeditious work flow for my LR Raw conversions. This included carefully evaluated and tested "initial Raw conversion" settings for all the files out of my 1DMKIV.
Now they decided not only to change the Process Version (PV) but actually to also change controls that do different things.
This means that I will now have to (1) re-train from scratch on how to use the software and (2) intensively re-work all my current catalog on previous processed images (...since the review states that the controls differ a LOT...) if I want my photos to be current with the most recent PV.
Even if I skip the reprocessing now, this is something that will inevitably be a problem in the future as I don't see Adobe indefinitely carrying PVs from versions to versions..I mean, only 5 years have past and they are already in their 3rd PV, so sooner or later this problem will arise.
You are mistaken. In fact Adobe has gone to considerable effort to not disrupt your workflow. Process versions are still supported back to 2003. I tested the beta on some old images and the Basic panel adjusts to represent the earlier tool set when the version is set to 2003 or 2010. There is no need to update your old images unless you want to take advantage of the new process tools. If your pictures are fine the way they are, leave them alone. You could even, gasp, set the process version back on new images if you want to preserve your old workflow, which seems to be important to you. Even better, you can create a preset using an earlier process version, selecting the Calibration checkbox in the process creation dialog, based on an image with the version set to 2010, and apply that preset to any new file imports where you want to maintain the LR 3 settings.
You could also just not upgrade, depending on how important you think the other new features of Lightroom 4 will be to you.