Well, aside from traffic passing successfully through the new tunnels, the command:
show crypto isakmp sa
will show the status of the tunnels (command reference). You should see a status of "mm active" for all active tunnels.
To see details for a particular tunnel, try:
show vpn-sessiondb l2l
Details on that command usage are here.
If a site-site VPN is not establishing successfully, you can debug it. It's usually useful to narrow down the debug output first with "debug crypto condition peer " and then turn on debugging level 7 for Ipsec and isakmp:
debug cry ips 7
debug cry isa 7 (debug crypto ikev1 or ikev2 on 8.4(1) or later)
Then introduce interesting traffic and watch the output for details. Remember to turn off all debugging when you're done ("no debug all").
