Knights of the Temple features very solid medieval combat, among the finest I have seen. It has a great feel and look to it. The atmosphere and sound is excellent, with many touches here and there that I personally thought were outstanding (such as when you die).
If you have no interest in the medieval era, in sword fighting, and in the concepts of nobility and holiness, then you probably won't appreciate the experience of this game. But if you do have an interest in those things, as I do, then you will be very hard pressed to find a better game of its type anywhere. This is a rare gem in my opinion.
It is not the 'perfect' game, however. It does feature a great deal of combat, and although there is a story behind it all and some excellent cutscenes, you will spend most of your time in the heat of battle and this can be a little tiring. It would have been good if there were more things to do, more options and so on, but it's still a solid experience (and far better in my opinion than the sequel, which has a lot more to do but is a little less refined combat and story wise).
Wield the sword of a holy Templar, and use it to destroy evil!