Flew GRU-JNB-GRU on the A330-300 both ways. Was lucky on the return as it looks like most of the week they've subbed an A343.
Overall, seat much better than the A343/A346. I was in 2K, which is one of the window seats with the seat nearest to the window. Feels like a mini suite - almost a bit tight to get out of but private. I would've preferred sitting a few rows back as there was quite a bit of action in the forward galley. Row 1 would be quite noisy. I found the seat to be hard, even with the small mattress pad. Ultimately didn't sleep that well either way, partially due to turbulence during the middle of the Atlantic crossing. Service was a mixed bag.
Happy to answer any specific questions.