I am definitely impressed with MSN maps on first use.
First thing that comes across is the load speed, it definitely kicks google out of the water, even though im pretty sure their servers must be loaded since they just launched. Another aspect that stands out is the smooth scrolling, another +1 for virtual earth.
They have also included some features such as "locate me":- ( cant say much since both google and microsoft cant find my house and simply give me the map of houston ), "scratch pad":- which remembers all the places you searched for and also keeps track of where you last left off using cookies.
MSN maps is brilliant, though I dont see myself completely switching to either service I will surely be using them both side by side while comparing the results.