I initially had problems with the link to MSoft but it downloaded and installed really quite quickly. Personally I think Google might soon have to play catch up with the high definition mapping, there seems to be more available on the MSoft site. On the negative side theres sometimes a fair bit of lag between zooming in and the display catching up, Google seems to have the edge there. But it's all still in Beta so who knows what will happen as time goes by.
I use IE7 and Firefox but I get a bit annoyed with Firefox it doesnt always have the ability to download some content. It was the same with this mapping, but I guess our Biil kinda made it that way, so it's not really the fault of Firefox.
The 3d mapping is tremendous, and some of the enhanced models theyre using like the Statue of Liberty are fantastic, Ive added a picture of it taken from the site, it doesnt give you the 3d feeling of the MSoft map but it shows you her ladyship.....