I worked with one Hennessy that was a nice sport horse-- good mover, lovely balanced canter, and jumped like a hunter. He was a fun horse to ride, but probably not an upper level prospect; likely would have topped out at prelim or intermediate, though he was great fun popping over training level stuff and foxhunting. You could canter him all day long with a smile on your face.
http://www.youtube.com/watch?v=z4hpYkgTi9A
Regarding Silver Tree: he looks okay to me. I’m not blown away by the photo, it’s not bad, but it doesn’t jump out at me as a potential sporthorse sire; though I might like him better in person. I’d have to see a lot of his offspring on the ground before I’d make a decision to use him; though I’d likely take a gamble on one of his kids off the track if it looked nice.