This is a campaign that could have been a good one, but that was unfortunately ruined by a bunch of small mistakes. Most of "Minamato's Quest" is well done, and would have been around the 3.6 range, except that a number of bugs that are impossible to overlook bring down the score.
Case in point: In the first scenario, you must safely bring Minamato and his army to your Wonder. However, due to a broken trigger or two, the scenario is impossible to win the way the author intended. You must simply sit back and wait for the time on the Wonder to run out. Also, the author states in the objectives that you will need to gain allies and units to succeed in your quest. However, I just made a beeline for the wonder, and arrived at my destination within minutes. The second scenario is totally unplayable, as it crashes a few seconds after the scenario starts. Things like this lead me to believe that the campaign was never really playtested.
However, there is a large number of good points for this campaign, such as good map design (for the first three levels), a nice story (for the most part, although the first scenario has none), and a large variety of scenarios, from quest to puzzle to battle to siege, all with a good number of triggers that keep it going (although most of the triggers do not work, or are very sensitive).
The Map Design is good for the most part, and is definitely one of the highlights of "Minamato's Quest". I wish that more people would put this much effort into their maps. However, it is a shame, as all the hard work that went into this campaign was nearly wasted due to the lack of playtesting. This could have been a good campaign, but it is only mediocre due to the large number of bugs that make it impossible to beat, and cause crashes.
Unfortunately, not as much effort was put into the last two scenarios as was the first three. In fact, the last two seem just like a Random Map with units and buildings thrown in... which is a shame. All told, this campaign is still worth a play, if only to see what it could have been.