Very good point Mistershine.
Maybe a delay of 5mins because some people I know will sign in and out multiple times over a short period.
Maybe once you'ved logged in it only tells you once when someone has logged in unless you was in a chat with them and they get disconnected unexpectedly.

That's really annoying. I have friends who will keep inviting me, sending me messages, party invites, then when I finally decide to play the game, it's full so I can't join or they already started. It pisses me off.

Delete your friends.

LOL, So true! The timing is flawless sometimes. I would do something i think is worthy of an acheivement, and bleep bloop...a friend signed in

-_- 

But it's hilarious sometimes when it happens, and i leave friends messages saying, "Damnmit you made me think i got an achievement! lol"

Dude, I'm quoting this!

Lol, same here, he's earned a spot in my signature's Quote of the week section

The only thing I hate is when I'm watching a movie through Netflix and I get the goddamn jingle and image of one of my friends signing on and off. It ruins the mood of the movie. :c

Is there a way to turn it off?

There is. Go to the Xbox guide (big button on your controller), go to the right and pick "Notifications" iirc. Just turn everything off.

lol, I have thought I've gotten achievements that I have not gotten - but I play a lot with my friends online and it's good news when I can stop being anti-social and game something other than alone (when I am that is), so it's like a win win I think.

Although Achievements are a little less healthy.