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.

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
FEC0:C0FF:EE00::11:2
            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