I'm running OS 4.2.2.170 on my AT&T 8310, just got an 8 GB card from SanDisk. Popped it in and its showing just under 8 GB of memory. Looks like its running well.
I would like to post that I bought 3 8GB genuine SanDisk microSDHC cards off eBay for 2 Alltel 8130 Pearls and 1 Verizon 8830 Worldphone and all the cards worked and are working flawlessly. I formatted the cards using the options/memory card/format function in each phone and afterwards they all showed about 7.6GB of useable space. (I know the Pearls are running 4.3 and I'm 90% certain the 8830 is.
Also, I HIGHLY recommend transferring data through the USB card reader it comes with versus the USB phone data cable. Transferring a 200MB video took about a 1.5 minutes through the reader, but about 7 minutes through the cable.