Since, as most of us know, Microsoft will likely make any meaningful or useful updates to Streets & Trips, I am giving Delorme Street Atlas another, more thorough evaluation.
BTW,
it looks like the "regular" version of Street Atlas is no longer available: http://shop.delorme.com/OA_HTML/DELibeCCtpSctDspRte.jsp?section=10120&minisite=10020 leaving the "PLUS" version as Delorme's only road mapping *& navigation software product.
One of the limitations of the "regular" version is that the address book is limited to 200 addresses:

...which is certainly a huge drawback if you're trying to import nationwide POI files like the 2,000+ record Home Depot locations POI file shown above, of which Street Atlas imported fewer than 10%. And what's even worse is that this limit is on the address book itself, not on how many records can be imported into it at one time.
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I've managed to get past some of the more clunky aspects of the interface that caused me to cut short my previous tests. It turns out that Delorme's "different" scheme for zooming out isn't all that bad once you get used to it. I don't like having to put the point at the edge of the map to make it turn into a pan tool, but as I just discovered during this evaluation, the CTRL key turns the pointer into a PAN tool. Still, that approach normally requires both hands (unless a mouse button is configured as CTRL-Click), so IMO what Microsoft did with S&T2009+ is better, since it requires only one hand to use it.
I have been somewhat pleasantly surprised to find that
Street Atlas has some of the POI search capabilities I described in this thread: http://www.laptopgpsworld.com/4931-find-nearby-places-route-ahead-see-their-icons-any-zoom-level
Aside from superior POI-related search features, Street Atlas also provides a limited range of adjustment for when larger, easier to recognize icons are displayed (S&T offers no view options like this). In Street Atlas you can choose to see the "Large Symbols" when zoomed out as far as this zoom level:

While it's great that
Street Atlas has much better POI search capability that S&T, from what I have found so far, it also looks like Street Atlas has far fewer POIs in its database... in some cases showing maybe half as many restaurants in a given area (that have been there over a decade) than S&T.
Street Atlas has much more fully developed navigational functions and a much better navigational screen than S&T: 
...and also has an "E-Z Nav" button that brings up a standalone-style set of buttons for common functions:
But Street Atlas has a clunky interface. Even after getting used to it, it's still inherently clunky and non-standard.
They also made some poor choices about which functions work in which tabs, and that does reduce their usability. Here's an example (though not related to a POI search) of one of their more egregious gaffes: the Street Atlas "Route" tab has a few options buttons, including an "Advanced" button that shows a list of all the route points
(nearly identical as S&T's "Route planner" including the 'delete' & 'move' route point buttons on the right):
But unlike S&T, Street Atlas does not allow any changes to the "Start" point or the "Finish" point from the list shown in the Route tab (buttons at right are greyed out).

Un-[frikin']-believable....
It looks like Marvin covered a lot of this in his review of Street Atlas 2010 here: http://www.laptopgpsworld.com/3888-review-delorme-street-atlas-2010-a so I don't want to duplicate too much of what he has already done. But I have a lot more screen captures that tell a more complete story about Street Atlas than you will see on Delorme's website. If anyone is interested, let me know and I will post them.