Let me start off by saying I love my PS3 and credit to you for creating an amazing console.
I have been an avid gamer for years and like most I've been doing most of my FPS gaming on a PC online/lans etc. It baffels me as to why you can't join a server that your friend is currently playing on. Now I know your buddy can send you an invite but this method isn't perfect and well most of your time is spent getting "full, game session is longer available" messages. To me it would've made perfect sense if you could hit triangle to view your friends, select your friends and then have the added option of "Invite or Join" instead of just having the former.
Will there be any chance of an update coming down the line to include this? Am I in the right thread to post such a query? Who knows cos I don't!