Rather than posting my opinion of MSN VE based solely on first impressions, I thought I'd get a little more familiar with it first, and now that I have, my reactions are mixed. Let's take it step by step...
General UI:
I personally think Virtual Earth wins in this area, although some may think otherwise. The ability to zoom in and out using the scrollwheel (or the touchpad edge) makes navigation just so much more natural as compared to using a separate slider control, and it's less jerky than Google's implementation. The "game panning" navigation, which kicks in if you use the compass-like UI element is also very smooth. MSN VE and Google Maps are tied when it comes to keyboard navigation though - the implementations are almost identical, although as mentioned earlier, zooming in and out using the + and - keys is smoother with VE.
Roadmaps:
There's no real comparison I can make in this area, other than to say MSN VE's color scheme is a little more subdued as compared to Google's brighter colors. Which one you prefer is largely a matter of personal preference. To me, the difference is small enough to make it insignificant.
Satellite imagery:
Ah, this seems to be a sort of hit-and-miss thing, where one does better than the other depending on your location. I found that here in the California region, MSN VE's satellite imagery is significantly better than Google's. The level to which you can zoom in is nothing short of impressive! VE uses the same imagery as TerraServer, which I've used before, so this didn't come as a surprise to me. However, when I jumped over to the New York area, the result was disappointing. Google offers full color satellite imagery here, whereas MSN VE only has grayscale images available, which aren't quite as clear either. Some people have also noticed that MSN's images might be older than the ones Google has acquired. The MSN VE team has announced that it is working towards acquiring updated images. All I can say here is that depending on your location, your mileage may vary, and vary quite a bit it may.
Layering and the Scratchpad:
Props to the MSN VE team for both of these unique features. They're extremely convenient for local search applications. I always found it a little irritating when my previous search results on Google Maps were wiped off the map when I searched for something else. MSN VE uses a layered approach, whereby it allows you to perform multiple local searches one after another and displays the results on the map using different colored flags. So if you're travelling, and looking for your hotel, and also want to find any chinese restaurants nearby, it becomes really convenient. The scratchpad allows you to add multiple locations to it, which is a handy tool to have if you're going on a trip and want to keep track of all the different stops you're going to make on the map, in addition to the starting point and destination. If I need to do local searches from now on, I know where I'll be going.
Locate Me:
This is another very unique feature originally developed at Microsoft Research that uses WiFi triangulation to determine your location on the map. It seemed to work really well in the Channel9 video, but for some reason, VE used the IP reverse-lookup method to find my location even though I had the little Location Finder app installed and running. So the best that it could do was to tell me I was in Los Angeles. Not bad, but nothing earth-shattering. Maybe there weren't enough wireless access points around me? This can end up being a really cool feature once it starts to work for everybody though.
The disappointment:
And this is the big one...really big. Big enough that I couldn't believe it when I first tried it. MSN VE has no driving directions! How could this not be the top priority? The single most important reason people using online mapping services is to find driving directions. Without that, everything else just becomes a novelty that will wear out sooner or later. From what I can tell, the base is there - anything that you search for has "Drive from" and "Drive to" links associated with it. The problem is that clicking either of these links, rather than overlaying directions on the existing map, takes you over to the old MSN Maps site, where the user experience is just sub-par. The banner ads on MSN Maps take up more space than the map itself! This is a real shame for an otherwise wondeful implementation. If anyone on the MSN VE team is reading this (and I heard they're looking for feedback on blogs), I really urge you to make this your number one priority for the Fall refresh! "Eagle-eye" view is incredibly cool, and it's something I know everyone is waiting for, but this is a far more useful addition that really needs attention.
To sum it all up, I feel that the lack of driving directions on MSN VE is enough to prevent me from moving away from Google Maps for now. I'll still start using VE for local searches though, since the implementation is just so much nicer. However, I see the amazing potential that VE has, and once driving directions, eagle-eye views, and updated satellite imagery are in, I'll switch completely without a second thought. Just not yet.