That's a rendering engine, not a complete game engine. When you go that route, you have to fill in the gaps for the other aspects of the game that you need: audio, networking, physics, and so on. There are plenty of open source libraries out there that you can cobble together to use with OGRE, so it's not that big of a deal. There are several pros and cons to this approach. One big advantage here is that you can mix and match libraries and not include anything you don't need, particularly useful if your game is limited in scope. One particular disadvantage is that you don't get the convenience of the built-in editors provided by monolith frameworks like Torque and Unity, and that's a big one for many types of games.
So I think comparing OGRE specifically with Torque and Unity isn't very useful. However, it is appropriate to compare the approach of using monolith packages with that of putting components together piecemeal.