With your amount of usage I would recommend a business class service where the same speed is delivered to each user rather then one shared speed .
Yup, the question is for anybody/everybody.
Latency: Yup, very important, but my 3M connection was capable of better latency than my FTTN connection since I am stuck with interlacing now. My 18ms base latency is fine for all that I do, so not complaining.
Upload: Yup, upload must not be forgotten but I was replying to a post that did not mention it. I went from about 1M to about 2M. I would like more upload but am not doing anything that really needs it recently. The biggest upload hit for me is that the Sonic FTTN VOIP will break up if the upload side is saturated. Only seen in testing so far but it is the biggest reason why I would rather have more upload. But note that proper QoS would also resolve that.
5 people doing 1080p: It sure looks like that could be handled by 50Mbps but it would be nice to have some overhead margin so 100Mbps would seem like a reasonable consideration.
And yes, the simplest answer to my question is having a lot of people. For residential customers I assume 5 Internet users is above average.
Thanks much for the replies. I am still not leaning toward considering FTTN X2 but I am open to changing my mind.