Ah, rugby! The violent majesty of unpadded, helmetless men laid low by fierce tackles! The heady not-passing-the-ball-forward action! The brawn-increasing effect of horizontally striped shirts! The sudden realization that this comprises the sum total of your rugby knowledge!
Let's face it: Hardcore rugby fans have this game already, and the question is whether others should buy a game they'll have to learn. Rugby 06 has a tutorial mode, in which you learn to scrummage, ruck, and line-out. Then Wikipedia can fill you in on what scrummaging, rucking, and line-out throws are, because the game assumes you already know. (That's okay; Madden 06 doesn't explain the counter trap.) So if the rest of the game functions smoothly, you should be able to learn as you go along, and soon you'll be off-loading the ball during tackles, scoring almost at will, and winning something called the Six Nations tournament, which is frankly pretty awesome.
And it does function fairly smoothly, albeit with some bad hiccups. Rucking and scrummaging—basically two different versions of contesting ball-possession—are handled by simply pushing the stick forward and pressing a button once the ball can be played. This seems unfair, as it's a complex and tense part of the actual game. Worse, you'll lose the ball far more often than not—for no discernable reason, even according to actual rugby-playing gamers. The computer opponent has magnet tackling and never gets a red card for clotheslining, but avoids your hits with ease. And the AI is near-telepathic, to the point where teams seem to move like schools of brawny fish.