I have been kicked to XMB one time, it was a day or so after the latest patch, 1.03 I believe.
I've been playing Starhawk since early in the beta, approximately November-ish.
I bought the game launch day and play almost every day, I have almost 200 hours since launch and only the one kick to XMB.
I can not recall the circumstances of the kick, just that the screen went black while in game, then a few moments later I'm at the XMB. I think the map was Cypress.
Normally I get a PS3 freeze and have to restart, but since the latest patch this has only happened once in normal games, but I can no longer play split screen. Every time I try split screen the PS3 freezes as soon as the second player's pod bursts open/hits the ground. This happens even in Homeworld with just the two of us, which should be offline.
Now that I think back..... I had 1 maybe 2 freezes when I first got the game, but nothing since. It has been pretty reliable for me. I think I may have been xmb kicked once in basin.... I don't fully remember. I believe I was flying. Sorry I am not more specific. But I figure better to say something than nothing. It seems to be a regular issue for some players.