When I started with GPS a few years back I was very annoyed that a company would actually put a year number to the title of their mapping product, even though the map data was actually 3 years old. But over the years I came to tolerate it, because the only other alternative to get the most recent maps would be to walk into a local store and purchase paper maps.
For explanation why 2 to 3 year old data seems to be the norm for navigation products read the following 3 page article:
When a software developer acquires navigable map data, already at that point the maps are not up-to-date. And then the software developer adds the data to a new version of software, new features may be added, software needs to be tested, etc, etc, etc. Many months may pass from the day software developer gets the "new" maps till the software arrives on the store shelves.
Every software developer gets already somewhat outdated maps. Perhaps the only difference is how quickly the maps can be put into a new software version and shipped to customers.
You have MS Streets & Trips 2006. It was released about 4 months ago at the beginning of October 2005. Comparing S&T 2006 to iGuidance 2.1, which was released some 12 months ago, I surprisingly see newer streets in iGuidance, which Streets & Trips doesn't have yet. That seems to indicate Microsoft acquires new map data earlier in the process of developing their Streets & Trips. IGuidance on the other hand seems to do it quicker. Still though, the difference is not that significant to the daily use of most of us in my humble opinion. Choose the product based on its features instead.
Here are some sample screenshots depicting newer maps of almost 1 year old iGuidance 2.1 and older maps of 4 months old MS Streets & Trips 2006 (both products use maps by NavTeq Corp.):
P.S. I do not have opinion on Detonator software. (Is it for your Ford Exploder? ;-)