Try before you buy! Especially if new to the series.
First of all, the game is too long and repetative. With 50 missions and not as many settings, you are basically doing the same missions over and over. Although the gurads do change thier routes, you get used the levels and will eventually be able to breeze though them with no real thought at all.
Secondly there are far too many missions that have absolutely nothing to do with the storyline. Although these can be good in some cases, such as the missions in which you need to kill everyone on the level, it does make the storyline seem pretty disjointed. By the time your at a level with a cutscene, you've forgotten what happened in the last one. I would also have like to have seen a bit more of Rikimaru from the old games in here, but all he really does is send you on your missions and turn up once or twice in cutscenes. Finally i did like the idea of the ninja customisation option, but with it having no real effect on the game, the points gained from the missions are much better spent on abilities, such as running along walls and dissapearing in puffs of smoke, and the ninja items.
All in all Tenchu Z was still a great fun game. With the usual dramatic and sometimes comical deaths of your enemies, many of which involve them gushing blood about 6-feet into the air, Tenchu Z will keep any long time Tenchu fan entertained. New players to the series however may be very dissapointed by the many technical issued this games seems to have.