Well that was a really cool change that came about after the maintenance on Tuesday. However, in the big picture for our guild, it doesn't really change much. We have some reserves still that we would like to get into raids, and the only thing this would do perhaps is allow us to see what players who would like to join Frostwolves are like - and they can see if our guild suits them.
What it will change is those guilds who are struggling on Garrosh and raiding numbers. Now if they can get their friends to help, it will be great! I think we'll see a lot of people getting Ahead of the Curve, which will be great overall for game morale, especially in the pre expansion slump. It might help some heroic guilds poach players from other players (which may lead to even more guild collapses as people sample the grass where they think it's greener) before people decide they want to make the big server change - at least this way they can try it out before they spend the money on a move.
I think this is a good change. After all, this is what it is going to be like when WoD comes - why not trial it out now and see how it pans out? And then, everyone will be used to raiding with this new change.
Guilds who don't have strong guild ties will be the ones who suffer - for example, those who can't wait to dump subpar raiders will pull in others cross realm to help them "get a kill". Those sorts of guilds may not survive as dissatisfaction sets in unless they still have a core of strong loyal members. Strong guilds will become stronger if the people they pull into a raid cross server like what they see and want to come across. I'm looking forward to hearing how people are finding it - after this week I'll find out!