OK, this is sort of an old thread, but since it got bumped up, I'll give my two cents.
I don't see much advantage for a car for what you have proposed. Unless you gave yourself an extra 4-5 days, you really don't have a lot of time to explore outside the cities. Although I agree that driving in Germany is relatively easy, Munich is a huge exception. If your hotel doesn't offer parking (and in the historic core of the city, only a few of the expensive ones do), good luck finding it. The whole ring of Munich right now is undergoing a massive re-organization, and this is causing severe traffic problems in what was never a fun place to drive anyway. Finally, A8 Autobahn that connects Munich with Salzburg is one of the worst for Staus (the uniquely German version of a traffic jam). What looks like it should be a quick trip can take several hours longer than expected. At least the scenery is nice, though. Traffic goes slow enough that you can get a good look at it.
I mostly agree that the scenery in Bavaria is no more special than many other parts of Germany (as noted by Chris). The exception, though, is south of Munich where you can easily see the Alps. No other region of Germany can compare to this, in my opinion.