Lightroom Tone CurveSome users have experienced issues when upgrading from Lightroom 3 to Lightroom 4. In certain situations, Lightroom 4 is automatically flattening out users’ Lightroom 3 Tone Curve point curve work, even if the photos are left in the old (2010) process version. If you are a point curve user and haven’t upgraded yet, I would suggest holding off until Adobe fixes this issue. They are very well aware of it.  If you have upgraded, keep in mind that Lightroom made a copy of your Lightroom 3 catalog and upgraded it, so you do have the option to go back to working in Lightroom 3 for now.  I would first check to see if you experience the issue by selecting photos individually and looking at the tone curve (not upgrading the process version).

For those of you who do not use the tone curve, I don’t see any concerns in upgrading.