If you want to display any IPV6-related BGP objects (neighbors, routes …) you can use the familiar BGP commands, but have to prefix them with show ip bgp ipv6 unicast. For example, to display the BGP neighbors active in the IPv6 address family, you would use show ip bgp ipv6 unicast summary command. I doubt you like so much typing (I don't, just entering the IPv6 addresses is enough for me); luckily Cisco IOS has aliases - just configure alias exec bgpv6 show ip bgp ipv6 unicast and (for consistency) alias exec bgpv4 show ip bgp ipv4 unicast.
Update 2010-03-12: Cisco IOS also supports show bgp ipv6 unicast command, which (at least) makes BGP ipv4-agnostic. You'll find numerous IPv6-related BGP details as well as advanced backbone designs and configurations in the Building IPv6 Service Provider core workshop (register for the online webinar).
With these aliases, the BGP IPv6 maintenance and troubleshooting becomes almost enjoyable:
PE-C#bgpv6 summary ¦ begin Neighbor
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.0.1.1 4 65000 18 21 11 0 0 00:12:49 2
10.0.1.2 4 65000 20 20 11 0 0 00:12:50 2
4 65100 984 1086 11 0 0 16:16:33 2
PE-C#bgpv6 regexp 65100
BGP table version is 11, local router ID is 10.0.1.5
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> FEC0::1:3/128 FEC0:C0FF:EE00::11:2
0 0 65100 i
*> FEC0:1:0:3::/64 FEC0:C0FF:EE00::11:2
0 0 65100 i
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