Lightroom 4 

 A great video of "how-to" in LR4, including how to save a JPEG snapshot from a video

http://laurashoe.com/videos/whats-new-in-lightroom-4/whats-new-in-lightroom-4.html

LR4 review - http://mansurovs.com/lightroom-4-vs-lightroom-3

Here is a list of some of the new features in Lightroom 4:

1. Updated Lightroom storage engine
2. New Image Process Version 2012 that unlocks new LR4 features (see below)
3. Better highlight and shadow recovery
4. New White Balance capabilities, including a White Balance brush that allows changing white balance selectively on images with mixed lighting sources
5. New editing brushes for noise reduction and moiré removal
6. Better GPS integration with maps
7. Extended video support, including limited video editing capabilities, playback and video export
8. Built-in soft proofing capability (previewing images for print)
9. Capability to create Photo Books/Albums
10. More online sharing options and integration
11. Ability to email photographs directly from Lightroom
12. Ability to import and convert LR3 databases
13. One click Chromatic Aberration removal
14. Ability to burn CD/DVD disks in Lightroom
15. Support for Nikon D4, D800, D800E and Nikkor 85mm f/1.8G
    
    

I was really missing the Fill Light and Recovery in LR4, but I found this on Adobe's website http://blogs.adobe.com/lightroomjournal/:

What happened to Fill Light and Recovery?

Recovery and Fill Light are popular and powerful tools. However, they also have some limitations. For example, Recovery can result in muddy highlights, and Fill Light can lead to visible halos at high-contrast boundaries. Furthermore, it is difficult to transfer the technology behind these controls to local adjustments.
With Process Version 2012 in Lightroom 4, we have introduced a new set of Basic tone controls that overcomes these limitations and results in much higher image quality. For example, the Highlights and Shadows tools are optimized for very high contrast images, produce much smoother highlight and shadow gradations, are available as local adjustments, and minimize halo artifacts.
We recommend starting at the top of the Basic panel and working down through the controls. Start with the Exposure and Contrast controls to set the overall desired image brightness and contrast. Proceed to the Highlight and Shadow controls, using them to establish the relationship of the highlights and shadows in your image to the midtones. If needed, fine-tune your image’s tonal end points using the Blacks and Whites sliders.  Note that Exposure, Contrast, Highlights, and Shadows are also available as local adjustments.
There is a bit of a relearning process, but once you have become used to the new controls we think that you’ll love them.  Of course,  you still have access to Fill Light and Recovery if you so choose by changing the Process Version to PV2010 in the Camera Calibration panel on the bottom right hand side.