I don't know why they would entrust Oz with the ring if he was going just by himself, but I'm glad they did. He (and Spike) were really good in this episode, especially Spikes mocking of Angel and the girl and Oz driving the van through the wall.
One thing I didn't understand was when they got Angel back, why did they want to get him to a hospital? He was only tortured, and while extremely painful he would still... umm live and not die. Don't you need one of only a few ways to kill a vampire?(staking, sun light, decapitation, etc)