As I may have mentioned before I frequent the Alternatehistory.com forum and a member started a new thread today that gave me the idea for this blog. Essentially their idea was that the RAF takes jet engines seriously much sooner and as a result they have jet fighters in the Battle of Britain. Now it's an interesting idea but the problem arose when the question was asked; 'how will the Germans react to this new development?' because the answer was 'they will just ignore it'.
This illustrates a problem that can creep in when you have characters who are definitely the heroes of the story; there's a risk that you pile all the virtue's and skills onto the protagonists and leave the antagonists as bumbling idiots but that's relatively easy to spot and correct. A slightly more subtle version that I have seen in a number of published works is that some of the 'bad guys' are good at their jobs but they are really good guys just on the wrong side. That is that competence becomes inextricably linked with morality and virtue; if the character is good at their job then they are morally good as well.
The real world of course illustrates that this is seldom the case; people can be truly great inventors, scientists, artists, or generals and yet be terrible human beings. You always need to bear in mind that most of the time the antagonists are every bit as convinced that they have right on their side as the protagonists do; and if you really want create a devious and twisted plot they might actually be correct in their assessment!
The other problem that can arise is what I think of as passive incompetence. Essentially this is what was happening in the example I gave at the beginning; the writer has such a clear idea of how they want things to turn out for the 'heroes' that the other side becomes simply props; they only do things when the protagonists interact with them. You can get away with that for a little while but eventually the reader is going to tire of antagonists whose only purpose is to demonstrate how awesome the protagonists are; they need to have an existence and a purpose even if it doesn't make it into the narrative itself...