It seems to be working quite well in terms of ISP choice (see my reply to cycomanic). And Chorus is offering up to 8 Gbps connections over XGS-PON, with most of the other fibre companies either also offering XGS-PON or working to offer it.
I suppose there are a couple of downsides compared to being able to use your own ONT, in that residential customers can't get SPF ONTs, and Chorus's XGS-PON ONT is quite large and not wall-mountable, which has caused a few people to hold out on XGS-PON offerings (they're working to offer a smaller one, but it got set back a bit, and they also won't start offering it until they run out of the old XGS-PON ONTs). But that's all quite minor (a residential customer wanting an SPF ONT is very niche indeed, as is a genuine need for a residential XGS-PON connection).
I suppose there are a couple of downsides compared to being able to use your own ONT, in that residential customers can't get SPF ONTs, and Chorus's XGS-PON ONT is quite large and not wall-mountable, which has caused a few people to hold out on XGS-PON offerings (they're working to offer a smaller one, but it got set back a bit, and they also won't start offering it until they run out of the old XGS-PON ONTs). But that's all quite minor (a residential customer wanting an SPF ONT is very niche indeed, as is a genuine need for a residential XGS-PON connection).