For Lightroom 3 users upgrading to Lightroom 4 or 4.1 who have lots of presets that are applicable in the develop module be cautioned. These LR3 presets will not have the same effect when you convert your image to PV 2012 (Process Version 2012)
The best way to handle this is to select your image in the Develop module in LR4. Next select the preset and click on the exclamation icon on the lower right of your image. Using the pop-up dialog allow the update version to execute.
Now you will need to make necessary modifications with the sliders in the basic panel as these are no loner the same as in LR3. Once you are satisfied with the results of your adjustments you can save this as a new preset.