This was exactly my experience. My iPhone struggled to understand me at times (albeit only 2 out of 20 times) - but the Nexus S (a fairly old phone) understood

This was exactly my experience. My iPhone struggled to understand me at times (albeit only 2 out of 20 times) - but the Nexus S (a fairly old phone) understood me 20 out of 20 times. It really whipped the pants off Apple - I was quite surprised. To see so many posts above say that Google Voice was far below par of Apple was a surprise to me. Note: I haven't tested IOS6 yet, so things may be different.