Since getting my A77 last September, I have use it extensively on two major trips to India and South Africa. I previously used my A900 with either the Tamron 200-500 or Sony 70-400G for wildlife work.
On the last two trips I have used the 70-300G which is not my favourite lens but it is significantly lighter and less bulky, I also took the 16-80 ZA and an old but favourite Minolta 24-105 for use on the A900 for wider shots. The 70-300G actually performs beautifully on the A77 missing some of the poor corner performance it shows when used on the A900.
In South Africa I decided to use JPEG only on the A77 so that I could use the very useful built in converter button (in camera crop tool) this enabled me to accurately compose and focus on the subject hand held at up to the equivalent crop of 900mm ( ie 300mm x APSc factor of 1.5 x 2 or 1.4) all handheld or beanbag supported on the window frame of a Landcruiser.
Some of my successful shots were captured at night on a night drive where the EVF allowed me to compose and focus accurately and very quickly.
I haven't used JPEG only for very many years so I was very nervous of the outcome but I was impressed with the results of the JPEG images taken in India with the RAW plus JPEG file settings, so I was prepared to take a chance and pleased with the results coming back with far more keepers than usual.
Some here complain about noise with A77 images and certainly as with the A900 unless exposures are spot on and post processing of poorly exposed images quickly produce noise. I processed all my JPEG images using my favourite Capture One software even though they were in JPEG format, most but not all of the C1 features are available for JPEG processing and saved to 8bit Tiff format for printing or storage.
Sony 12 bit images are not as robust as the 14 bit images produced by other pro cameras, and prone to developing noise if over processed. Compared to my 16 bit Leica DMR images they are positively thin!
Both the A77 and A900 are tough enough to withstand the rigours of bouncing up and down over very rough terrain, on and off safari vehicles in dust and sometimes wet conditions, my A900 is now over four years old and still going strong.
I doubt if my Leica R9 and DMR back would have survived too much of this treatment and I have both Sony's, a stack of excellent lenses and a wad of spare change from the proceeds of my Leica sale!!