Or is it just my previous experience with MapSource that makes me feel this way!!
I don't think so. I don't think it's just
your Mapsource experience.
The Mobile PC interface is designed primarily for standalone devices with touchscreens. The interface is, by design, self-limiting. It works great for navigation and quicky "find-and-route" use .. just the sorts of things you want to be able to do quickly and easily with a handheld nav device. But not so much for trip planning and creating complex routes, eg. vacation or business routes with multiple forced stops along the way.
That's where Mapsource really shines. It's great to be able to just click on the Route tool and start clicking on the places you want to stop. Or click on the start and end points, then start manually typing in Via points into the list and rearranging them to suit yourself. Mapsource is definitely the superior tool for trip planning and complex routing.
I agree with you completely that not including the ability to use Mapsource with the included detail maps is a shame. But it's not new to Mobile PC. You have the same issues with any of the Garmin products that ship with precompiled maps in memory or on flash data cards. The only reason you really notice the difference with Mobile PC is that a) you understand the potential that having the nav "device" running on the PC could provide and b) you have already been contaminated by Mapsource experience.
As long as my use of my laptop for navigation purposes is trivial (it's so much easier to fit my Garmin iQue 3600 PDA/GPS into the vehicle), I expect that I will depend on Mapsource and nroute because I can use all the maps installed in Mapsource for navigation in nroute. And I don't even have to compile and transfer them. The map display isn't nearly as pretty but the convenience of everything else more than offsets the gorgeous display of Mobile PC. Of course where City Navigator North America NT2009 suits my purposes, I'll probably still use Mobile PC ... purely because of that lovely map display.