It's an excellent addition. Though my personal fave is to take your target down as he walks past the bench you're sat on. The animation that results in is superb.
I think the assassinations from hay piles is my favourite addition, it's not only effective but always makes me smile for some reason.
Spot on - I only did that once, and only by chance...I just saw "assassinate" pop up while hiding and couldn't resist. The best animation, bar some of the two-handed weapon counter kills.
Tenchu Z was awesome. Particularly in co-op. It was all kinds of out-dated and broken, but the stealth kills were great. I dream of a new Tenchu with ACII quality graphics and co-op. That would be a GOTY for me right there!
That would be so fucking sweet.