For what it's worth, FX has been doing IPv6 natively on pretty much all customer connections for several years, both the WAN product and the ISP product.
Standard prefix allocation of /56, static allocations.
As part of that we have native V6 enabled DNS servers and NTP servers available as well if you want to use em.
Not all customers (or even most) are using it, but it's there and ready to go when they want to, and doesn't require any additional provisioning because it's already done as part of the initial build.
Operationally wise, there were some nasty bugs in some older IOS versions which have been fixed in the more recent releases which were potentially a show stopper as far as using IPV6 on your management network - the SNMP and TACACS support was busted, so if you're using ME3400s and 891s and so on you'll need a pretty recent IOS if you want to go V6 management.
Statistics wise I don't have solid numbers, but it's a non-trivial amount of v6 traffic passing over the various networks. There are a few graphs I can see which have peaked briefly over 100Mbit/s of V6 in the last week. There are OIDs available from some devices which will give you a seperate v4/v6 breakdown if you're trying to graph it, but not all have that feature, it's a tricky thing trying to measure this but it does seem to be on the increase.
Cheers,
Blair