Lightroom 4.3 has several improvements, bug fixes, supports many new cameras, lenses and has added several tethered cameras to the list. The new features listed below are from Adobe’s website.
Adobe downloads can be found on Adobe’s website.
Here’s a list of the bugs fixed in Lightroom 4.3 from the Lightroom Blog
New Cameras supported in 4.3
Canon EOS 6D
Canon PowerShot S110
Canon PowerShot G15
Canon PowerShot SX50 HS
Casio Exilim EX-ZR1000
Casio Exilim EX-FC300S
Leica M-E
Nikon 1 V2
Nikon D5200
Nikon D600*
Olympus PEN E-PL5
Olympus PEN E-PM2
Olympus STYLUS XZ-2 iHS
Panasonic DMC-GH3
Pentax K-5 II
Pentax K-5 IIs
Pentax Q10
Sony DSC-RX1
Sony NEX-VG30
Sony NEX-VG900
To get the update: Inside Lightroom just click on Help –> Check for Updates
The download is 700MB+ – Once downloaded you can complete the installation.