Bought this entirely on hype alone from Amazon, as it's hard to define the genre and thus tell if you would instantly like it before seeing what it is. I was not disappointed. Going to break it down into a few sections here for detail.
Absolutely excellent use of 3D, stunning effects. I notice the nintendo made games know how to make and use the 3D effects very well whereas the third party 3D is lazy or pointless to turn on. The stand that comes with this makes it very easy to hold it perfectly still for the 3D too so I find I have it on a lot without getting tired. I'm guessing a lot of the eye-tiredness from 3D reports when the 3DS came out was because it's impossible to hold it perfectly still so your eyes always had to adjust slightly and were working hard all the time. With the stand it really takes a lot of the strain out of your eyes.
Stand that comes with the game:
Really nice simple product, folds right up again for easy storage and feels a lot sturdier than I thought it would be. It keeps the 3DS very still for the 3D whilst still allowing good access to the controls, I find myself using it for other games like mario land and even drawing with the swapnote.
Just want to talk about the controls briefly because the professional reviewers are very harsh on them to the point people might not give the game a chance. I just wanted to say yes, they were weird to get used to at the start, in the beginning I could only play on the 2.0 intensity level and had difficulty even with that. But by the time I was playing the 3rd level I could put it up to 5.0, by the 8th level I could play on the hardest intensity for a good few levels, and I don't have experience with any game like this. My usual game type is just rpgs, total shooter noob. So yeah, if you play the game more than the 5minutes the reviewers probably played of it, you will realize that the controls couldn't be done any other way, and that they are quite easy to learn. For lefties you will probably need to rebind the controls in the menu or get the circlepadpro though.
Offline Solo Play:
There really is so much to do in this game, the music is really well done, the characters talk all the time. It's very cheesy but you get used to it, full voice acting is such a luxury that I prefer it to a mute game even if the one-liners make me groan! Each weapon type has a completely different play style attached to it so you can really play it however you like. The story is engaging and every time you think the game is over there are many more chapters/things to do. There are a ton of unlockable achievements and weapons to aim for. I'm very impressed with the training area, you don't have to go into a level not knowing how your weapon manages, you can test it out in a safe training area where you won't loose any hearts.
The online play is very engaging and fun, you can go 3v3 as a team or 6man free for all. The different weapon types makes it very easy for a new person to still get some kills in, especially on 3v3 mode since all the attention won't be focused on you. You can get up close and melee them or just pick a weapon that lets you snipe people from miles away undetected. It's very easy to train as well if you are worried about diving in, you can play nearby mode against the cpu and adjust the difficulty. There are no penalties for loosing online either, and you can get things just for competing so don't be timid about it.
Overall score and conclusion:
I would give it a 9/10
I only dock one mark because a 10/10 scale would mean that 10 is the best game ever, 6-9 are awesome games, 5 is a decent game, and below 4 are bad. I despise the current 100% scale that most game magazines use where anything under 90% is a terrible game that you shouldn't buy, it's just plain stupid.
Because of the difficulty level and scaling, it's pretty much suitable for anyone like 10-90years old, I know it's 12s rated but honestly any sexual/flirty references are extremely mild, the Simpsons are far worse. It's probably rated 12s just to cover online play, even though you can't talk to anyone or receive messages I guess there is a tiny chance someone would have a non-pg name, but I haven't seen anything dodgy myself. It's a really great game, it looks really silly and my friend was laughing about how childish some enemies looked, then I turned the difficulty level up + gave it back to him. He wasn't so happy a flying nose killed him! You have the options to make it fiendishly difficult for the mid twenties buyer, and easy for the younger child. Though lets face it the younger kids now play far more games than we did, they are probably the experts!