Lightroom 4 by default uses Process Version 2012 (PV2012) - and doesn't have a Fill Light slider. Also the Contrast slider algorithm was changed so +17 in LR 1, 2, 3 is not the same as +17 in LR 4.
However, if you open the LR 4 Camera Calibration panel, at the top right of the panel you can change LR 4 to PV2010 - used by LR 3 - which changes the Basic panel sliders (and algorithms) in LR 4 to those used in PV2010.
Adobe Photoshop Lightroom 4 * Process versions