Here's an honest review of this game, which seems to draw opinions from the polar extremes...
I think Tenchu deserves a score in the 7's for this reason: it's not trying to be something it's not. Tenchu is a stealth ninja game, with over-the-top kills n' thrills. It's not trying to reinvent the sneaker genre, which has been well advanced by titles like Thief, Hitman, and Metal Gear. Rather, think of Tenchu Z as a lighter, "arcade" version of the titles I just mentioned. It's not TRYING to be the killer app for the sneaker genre, so stop criticizing it for not being that. Stop comparing it to Gears of War. It has NOTHING to do with Gears. Comparing Tenchu to Gears is comparing apples to oranges, period.
The final straw is this: Tenchu Z is going to appeal, quite strongly, to a niche market. If you like the Japanese "angle" on theatrics, found in a lot of action-based anime, with cool character angles and poses, and if you like the idea of being a ninja and using stealth to kill IN A SATISFYING, arcade-like way, this game is worth looking at. A major lament is about the game's graphics, and I'm going to agree 100% that the DEMO level somehow feeled wrong. I bought the game and can say the richer levels really do a good job of making you believe you're in feudal Japan, and there's very subtle, atmospheric touches that add to that - look closely at the ground when the clouds move overhead on an overcast night...there's a subtle twinkle to the ground that's enhanced when you cast your shadow over it. All these add to the atmosphere of sneaking around, and being a ninja...For comparison's sake, Tenchu Z's visuals are at the level of Ninja Gaiden for the XBox, which is not poor. But it's not Gears. And FromSoftware is fine with that. And I'm fine with that.
Tenchu Z is a game that is comfortable with itself. It's comfortable not trying to top Gears of War's production values. It's comfortable not trying to create an AI system that can trump a Snake or a Sam Fisher. From Software stuck to its roots in making an enjoyable, borderline-ridiculous-when-performing-fatalities game, and you know what? It's fun to play. I'm entertained by it.
I think the burning question is whether this title is worth the $60 + tax price tag, and I'm going to say here that I don't believe it is. I happened to have about 5 or 6 old PS2 games lying around to bring the net cost of Tenchu Z for me to around $30, which I feel is about right for this game. After playing it for a bit now, I think I could comfortably pay $40 upward of $45. Do try to rent it or get it at reduced price from eBay - if you fall into the niche described above, you're gonna love the game.