I'm finally getting around to writing this, after so many CC members have helped me with other trips! We sailed out of NYC in May '07. Embarkation was very easy, although the computer systems had "crashed" so everyone was checked in by hand.
The Miracle was a lovely ship. Our "obstructed" view balcony room (a bump-up from oceanview, my roomie was a past Carnival cruiser) was nearly unobstructed---the only "obstruction" was up to knee-level....and as I don't normally lay on the floor to watch the ocean, it wasn't a problem. :) When sitting normally in a chair, there was no problem watching the water.
The room was perfectly sized for two girls in their early twenties. We did, however, bring a shoe-organizer to hang inside the bathroom door, which helped hold suntan lotion, hairbrushes, etc. Two twins in a balcony room have about 1.5 feet between them, if you were wondering how space was organized.