Adam Bullied's recent post about competitive analysis is really good, but it's missing an essential point that technology companies frequently overlook: Companies compete, products don't.
That's not the same as saying that product comparisons are worthless. Of course it makes a difference that Product A can do more than Product B, as long as Vendor A and Vendor B are in the same market. Often, because of the complexity of the market, as well as its immaturity, technology vendors overlook the second part of that principle.
Similar products may not ever bump into each other because of accidents of geography. Ichitaro, the big competitor to Microsoft Word in Japan, has practically no international market. At other times, analogous products burrow into particular vertical niches so deeply that they never see each other. The specialized document management products you still find in the biotech, financial services, and legal markets theoretically could compete with one another, but don't.
Of course, a potential competitor might become an actual one, jumping across geographical or vertical boundaries. However, even if that were to happen, two companies in the same business might have radically different business models, in which case, the competition between them may be more apparent than real. For example, Singularity certainly has products to support Agile development, but they also do a brisk business in selling consulting and training. (Their Agile approach to BPM is particularly interesting.) In contrast, VersionOne is more of a product company. Both are trying to serve Agile product teams, but to what degree do they really compete?
A competitive analysis that doesn't include the details about the competitors has very limited value. The real threat may be the vendor that has a weaker product, but has a greater ability to market and sell to your customer base. What profiteth a vendor that builds a superior product, but loses its market?