I'm not trying to be the Gmail police or anything, but if you want an invite please copy and paste the list and add your name to it, if you don't then it gets very confusing for those that have invites to give out and you may get people who jump in frount of you.
The same for people who get an invite please colour your name in otherwise you may be taking an invite from people who still haven't had one
As for when you get invites I'm not to sure I've been using mine since I Richard sorted me out and I still cant invite people. I'm guessing they release a new batch of invitations as and when the servers can cope. All I need now is an invertation to Orkut and I'll have the set
Edit - Beaten to it by a turtle and a supply teacher, wheres my cyber gun?