The group window is good for organizing roleplaying (not roleplaying in, as it should never be used for), but it is limited due to the fact that only the leader can invite to it, and crashing/logout requires a reinvite. This is a pain if the leader of the group crashes.
What I would like to see are more advaced options for creating a group that are like in guilds.
A. Add the ability to asign more than one group leader. Only group leaders would have the ability to kick players from the group.
B. Add the OPTION to let anyone in the group invite more players to the group, leader or not.
C. Logout does not kick you from the group, and relog auto-rejoins you to it until you leave the group, it disbands, you are logged out for several days, or you are kicked.
D. Mute group OPTION. This is so just the leaders can speak. Used for RP purposes.
E. Add the OPTION for group leaders to see the exact positions of other players.
F. Add the ability to join secondary groups. A limit of three groups per player would be good.
G. Tying in with F, the OPTION to name groups. Otherwise, each group would have the leader's name. Example: 'Hyuken's Group'. Or, if renamed, 'Barflies' or 'Tavern regulars'.
Groups would be more like unofficial guilds and 'clubs', and as such, you can belong in more than one.