The problem with reviewing High Voltage's The Conduit is that it's impossible to do in a vacuum. Depending on where you're coming from, you're going to have vastly different reactions to this game, so I'm going to do my best to talk to everyone.
For FPS fans who only own Wiis: First: What the hell is wrong with you? Second: Yes, you should absolutely buy The Conduit. While the Wiimote may lack the fidelity of the mouse and may not feel as comfortable as a thumbstick, it definitely works. It's also really satisfying to have a targeting system responsive enough to work without a bunch of auto-aiming assistance (it's there if you need it, though, in the form of a lock-on button).
There's a wide range of cool weaponry from an alien rifle that augments your powers of sight in place of a scope (a nice touch) to old classics like the shotgun and pistol. Less impressive are the underpowered grenades which are stupidly mapped to shaking the nunchuk, meaning: 1. The action of throwing one usually messes up your aim; and 2. You're guaranteed to set the controller down to answer the phone or pet your ferret and accidentally blow yourself to high heaven at least once.
But if you're starved for FPS action, it's not going to bother you. There's a lot you're going to like, and you'd be crazy not to pick this one up.
If you're in the market for a new multiplayer shooter: Again, you're probably going to find something to like here. Now, The Conduit may lack a lot of the depth and bells and whistles of most modern FPS titles on beefier consoles, but there's a lot to like in the simplicity of The Conduit's team deathmatch, free-for-all and objective modes. You may have to fight with the controller a bit more in the multiplayer, but you'll know that everyone else is in the same boat, so you really don't have an excuse.
If you want something that feels a little more classic, i.e. an updated Perfect Dark, I think you'll be pleased, assuming you can get past the big loss in graphical fidelity on Nintendo's little white box.
If you're a multiplatform FPS fan: See, this is where it gets a little tricky. The Conduit is a fine effort, but if you've been feasting on Call of Duty, Halo, Killzone, etc., there's no way this isn't going to feel like a sack lunch. Using the Wiimote might be novel for a few minutes, but once you get past that there's not a whole lot of reason to come back, least of all if you've got a lot of other things to play.
In its defense, The Conduit has a cool dynamic which has enemies pouring from literal monster closets (the titular "conduits") until you destroy the portals. This has you constantly weighing the benefit of fighting an enemy or trying to blow past him to close the door so he's the last one you have to kill. Not world changing maybe, but it's fun.
If you're worried about it being a kiddie game or more casual, you can put those fears to rest right now. The Conduit gets tough fairly quickly, making a switch to the easiest difficulty setting pretty tempting. It's not for babies, let's put it that way.
The problem is the good ideas dry up far too early. The big gimmick is the A.S.E. -- or All Seeing Eye -- which you'll occasionally have to hold (in place of a weapon) to hunt for invisible switches on the wall or disarm invisible mines (which the A.S.E. always alerts you to, making their invisibility pretty useless). It's just all so boring. Stumbling around looking for randomly hidden stuff never feels like a challenge, but rather a simple waste of time.
Environments look pretty good for a Wii game, but are still kind of drab and rarely reflect the Washington, DC setting. Weapons fare better, though most look like last-gen Covenant and Spartan tech.
When it's eventually bargain priced, it may be worth taking a peek at, if only to see how the Wiimote is implemented. But for now, if you've got the whole scope of the gaming landscape to choose from, it's pretty hard to recommend.