The average user will notice the lack of IPv6 when a CGN is put in the IPv4 path and things like port forwarding stop working. For some ISP's that is now. For others it is in the future. Until then you really shouldn't notice whether you are using IPv4 or IPv6 to reach another site or how you are reached. If you do notice then the ISP / OS vendor isn't doing their job properly.
Hopefully the ISP will take away the IPv6 knob and just deliver IPv6 to everyone in the near future. There aren't many IPv6 only reachable destinations yet but more are coming as more ISP's switch over to using CGN to deliver IPv4.