The game I've been waiting for all along for the Nintendo DS - But it might not be as good as it looked at E3 2005.
The key different between the demo and the actual game would be rather many, the general visuals have been improved, sharper textures and so on, new interface, new weapons and the Power Beam does now have unlimited energy and isn't full-auto anymore but bursts and holding the trigger a little longer will charge up the Power Beam like in the GameCube version(s) of the game.
Something that people seem to not have a too good grip on is the controls of the game. But it runs great if you've held a pen before in your life but it takes a little time to get into in the full game, the demo was a bit more approachable - but for those who find the original DS stylus too small would diffinitly get the Nintendo DS Lite, that will solve some of that issues. The controls is precise, once you've got used to it and the learning curve varies from player to player but for me it took about a hour or two, not the general controls but making more succesfull weapon-changes and aiming around without having to accidently happend to change weapons in the weapon-bar up the screen.
The story and single-player game itself is horrible, slow and has constant frame-rate issues. Everything will go over and over again, you'll fight the same bosses multiple times but you'll have to do so with the latest weapon you've found which have led you to the boss in any way. There's no real moments when you will actually enjoy the single-player, it's not feeling like an actual Metroid game but more as the cheap Golden Eye: Rouge Agent game for the DS. But there's one thing that is pretty nice with the single-player, and it's not the gameplay but the smaller cinematics in the game which is really high-res and is running and looking awesome - too bad the people working on the cinematics haven't used the 1cm blank space between the screens on the DS but worked it like it was a regular video for any unit, very unproffessional and frustrating.
The only real reason why you would like to play through the single-player is if you're not having a WiFi Router at home or accessable closely where you'll unlock charathers for you to use in the Multiplayer game. But if you have a WiFi router or connection at a hotspot you'll be able to get those charathers from winning over the opponent playing with that specific charather.
Even how awful the Single-Player might be this game is still focused around the Multiplayer. And as they said at the E3 2005 this game is surely the best possible Multiplayer experience for a handheld. It plays really well online using WiFi but runs a little slower over local wireless play and Download Play but it's still a good time. And the new charathers in the game sure spices up the game, seven different charathers all with their unique alternative-forms and affinity weapons but some plays out to be really bad balanced. For example, the most hated and crappy-balanced charather, Sylux, he's stealing life from the opponent while using his affinity weapon and when he starts taking damage he'll probably turn into his Alt-Form and circle around the map with his over-powered alt-form - and more than that there's also Trace which has the affinity weapon of handeling the "sniper"-weapon, Imperialist, which will kill a player with a well-placed headshot and he'll also camouflage himself with the background gaining a even more bad sniping position, and just as Sylux this fellow also have a annoying alt-form which is often used just to "alt-spam" around the map. If those two charathers would have been wiped out of the game or modified it would all be a epic close-quarters fight with outwise pretty greatly balanced, unique charathers.
With pretty much bad said about this game it's still great - the single-player game is there for those who might like to check it out and the multiplayer offers a varity of different modes of play, new charathers, many different maps, good WiFi support and also offers Download Play for those who would like to play with some other DS owner which haven't bought the game - but with a decrease frame-rate but it's still running fairly solid on 1vs1 games but less good on 4-player games, obviously.
I would recommend this game to any FPS-loving DS owner and found that Rouge Agent wasn't their thing, even those who might have liked the Rouge Agent for the DS will surely find alot more to do here.