My review so far:
You can't just play it for extended periods of time; you have to wait for the clouds to regenerate (45 minutes for 10 clouds at the beginning) before you can go hunting again (or you can spend 5 play coins to regenerate the clouds instantly, but you can only do that three times per day). You can go when there's only a single cloud, but the rewards aren't nearly as good. Once you collect enough energy from these clouds, you can trade them in for upgrades for your equipment (more clouds at once, faster Pokemon catching, etc.)
It appears that there's a plot of some kind - There's some rare Pokemon that this girl wants you to find or capture or somesuch, but as of yet, she's not sure how to find it. How to help her figure it out? Collect energy from the dream clouds.
Waiting for the clouds to regenerate is irritating - it's a mandatory break from the game. Other interesting things to mention: the AR does nothing. You can see the room you're in. Whoop-de-doo. As of yet, there has been zero interaction with the environment (at least with the other AR games like Face Raiders or the target practice AR Card game, targets would hide behind the background). It might as well have a completely computer-generated environment. I'd rather be in the world of Pokemon Snap or Ranger than my spartan dorm room. Another irritation - the game is only in 2D. Kind of a strange move when the game is for the 3DS and using augmented reality. Finding the clouds is a mind-numbingly simple task - just turn around until you find a cloud. Maybe you'll have to look up or down a bit. If you're an idiot and can't find a cloud, an arrow will point in the general direction you should look.
The only challenge I've encountered so far is catching a Pokemon (or an item that a PKMN dropped)... and at these early stages of the game, I'm very hard pressed to call it a "challenge." Hold down A, aim at the dodging glowy energy ball. Succeed at aiming at the energy ball for long enough, and you catch the Pokemon or item, which can then be transferred to Pokemon Black 2 or White 2, neither of which I own.
I'll keep playing for a few more days out of dogged persistance - see if it becomes any more interesting... but at this point, it's pretty much worthless. The Pokewalker provided more entertainment for me than this game has so far.