Ikkitousen is loosely based on the infamous Chinese novel, Romance of the Three Kingdoms which is set around 200 AD. As a person who knows quite a bit of the history during that period, I find easy to understand the relationships between characters and what the anime is trying to bring out. But I must admit it will be quite difficult for an average person with no background to try to understand what is going on in the story.
So before any further rating of the show, I would like to give a bit of advice to those who plan to watch this. IF YOU HAVE NO INTEREST IN CHINESE HISTORY (though rather twisted if you ask me), AND IF YOU ARE JUST TRYING TO DIG OUT SOME HEAVY FAN SERVICING ANIME, THEN THIS IS NOT FOR YOU! You might as well go watch hentai instead.
Yes, I agree that the fan service is very abundant (ridiculous is the term I would use), but I don't see the point in watching this if fan service is all you are looking for.
Story:
Trying to make a modernized version of the ancient war in China was a good idea to begin with. Though trying to retell it (even a small portion of it) in 13 episodes is just too much a task. The concept of the story is simple enough if you know the history.
At the end of the Han Dynasty, the government became corrupted and the local governors and warlords took over and began building up their power. Which in our case, the local governors and warlords are nothing but the seven schools. At the end, three overlords eventual dominated China resulting in the period of the Three Kingdom (which was explained at the end of the anime). Here are some links if you are interested.
http://en.wikipedia.org/wiki/Han_Dynasty
http://en.wikipedia.org/wiki/Three_Kingdoms
I rate it 7 because I don't find it very original, and messing up the genders of the characters in the Romance of Three Kingdom is just...wrong. Oh, and I really don't see much point in all those street fights.
Art:
Nothing too fancy...don't expect too much from it, after all it is made in 2003. But it is still decent for its time. Note that I am rating it based on the year of its production, NOT by current standard.
Sound:
I like the OP but everything else is just what one would call "standard" in the anime industry.
Character:
I can understand that the producer tried to build up some character introduction/developments but mostly ended in failure. That is not to say that they did poorly, but rather it was just too much for 13 episodes. (One got to understand that the actual cast for the Romance of Three Kingdom is ENORMOUS, the producer handpicked a very few exceptional ones only)
Enjoyment/Overall:
I don't recommend Ikkitousen to people looking for fan service. It is better for you to watch hentai. Seriously, there are more than enough scenes in Ikkitousen that are on par to hentai. However I do recommend this to fellows who might want to see how the story of Romance of the Three Kingdom can be turned into in a modern day Japan. Overall, I enjoyed the anime and had no regret watching it. In fact I might rewatch it after finishing Ikkitousen: Dragon Destiny and Great Guardians.