This game is actually quite awesome.
If you've never played Battle Network it's basically a Mega Man RPG which couldn't be any cooler if it tried to be. I honestly loved this game. It's innocent, but still holds true to the Mega Man universe, and even uses some of the old music.
Basically you have a tomigotchi type thing which is Megaman.exe. You can "jack in" to almost anything, and then megaman battles viruses on the net. This is where you'll recieve your random battles and level ups. The fighting is not turned based like most RPG's. Instead you get battle chips (cards) and use them to fight. You can either combine like letters or like attacks to do more than one. The battle system is actually quite fun and rewarding once you get used to it.
The music is happy and a lot like you'd expect fom the megaman series. It's relatively easy to play and is a fun kids game, but don't make that turn you aside if you're not a child. Any fan of mega man or RPG's will find themselves having an enjoyable experience.