This game is literally a blast. I had fantastic fun with the 1st Campaign and having a fair bit of challenge in the 'Advanced' campaign. Advance Wars is the epitome of a great portable game. While the visuals are not stunning, it is cute, bright, clear, and 'fun' to look at.
The compulsory training (13 in total) brings the new player up to speed on control and basic tactics. Yes, that's 13 training missions and every mission is useful and educational.
The main campaign mission is linear (goes from point to point) but branches out depending on which CO (commanding officer) you choose. The battles/conflicts have sufficient variety to keep you entertained (land, naval, air, etc. combination). The landscape design is particularly excellent and does have a significant effect on the tactics/CO choice. The missions are not easy either and offers a good challenge. Once the 1st campaign mode is complete, 'Advance' campaign becomes available which is much much harder than the normal campaign (you are severely outnumbered, out-financed, and out-gunned).
In addition to the main campaign mode, there are War-Room (single conflict scenarios against various opponent CO) & multiplayer modes. The total number of scenarious are staggering (I estimate about 100+). Some scenarious are so big that it would completely fill about 6 GBA screens and you have to pan back and forth. You can even design 3 of your own maps and scenarios! Multi-player option is a blast to play. You can play with 1 GBA to up to 4 GBA's. I played a 2 player game on 1 GBA and it lasted about 2 hours for a very simple map. I figure it would easily consume 2~4 hours on more complex map.
Every conflict you complete successfully, you are awarded with coins, rated on your ability, and sometimes even promoted (starts at rank 100 I think). I purchased the game last your when it first came out and although I have not played it to death, I have put in good 40+ hours into it. And I have only made to rank #83! The good thing is, I still find the game challenging and fun to play.
If you like strategy game, nothing else on the market can beat Advance Wars. Combine that with an excellent price and you have a sure winner. I have heard few good things about Mech Platoon so I plan to give it a try. Soon to be available title, 'Tactics Ogre: Knigts of Lodis' also got my interest no Advance Wars will see some competition finally. Still, you cannot beat the joy of pounding on a trasport ship with a battery of rocket launchers.
Visuals: 9/10
Gameplay: 10/10
Replayability: 10/10
Depth: 10/10
Difficulty: Hard
Overall: 10/10
Did I say a quick review? Oh, yeah, I did.