Lol i think the people who are complaining about this don't know what the Xbox guide button is.
Its useless now since we can run the entire OS without disrupting the game.

What if I'm in the middle of an online match and just want to quickly invite someone to a party, won't that disrupt my match and kick me out if I hve to exit the game...

You're not exiting the game you're pausing what you're doing, it would do exactly the same as what pressing the guide button would do.

microsoft already showed at their reveal in may that you can switch from game to the whole dashboard and do everything you like and switch back to the game now. people complained about microsoft because they showed it and now everyone asks if you have to cancel the game if you want something like inviting friends now.

I use this button only to pause videos that can't be paused by clicking on start button.

I agree. This seems like a pretty good idea to me. I expect the same with the ps4. 

Well the PS3 was like this so I'd hope the PS4 was too lol.

You really don't think that being able to switch instantly between games and apps is better than having to completely shut down a game every time you want to check something then starting it back up again?  Okay.  I, however, look forward to it.  To each their own.

I guess it's good if you don't lose progress and can return to your game. I did like the guide though :(

It was but you couldnt go into the PS Store or a number of other apps without having to close the game. The Vita is a step further so I dont think this will be an issue with teh ps4. Multi-tasking is one of the main features of both nextgen consoles.