I just tried it...pretty simple...log in with your Google ID, browse apps...pick what you want, verify your phone and carrier, and the app is uploaded immediately to your phone. It also shows you what apps you already have, although I didn't see that as 100% accurate...apps downloaded from sources other than the Market won't be there.
Not surprisingly, an emphasis on paid apps...this is supposed to generate cash, like Apple does by the fistful.
One thing to be aware of...the Web based Market doesn't know what phone you have up front...for example, it showed me Adobe Flash being available for Install, even though it won't run on the V. However, when I hit the Install button on the Web site to begin the upload, it did see my phone choice and had it grayed out. Hopefully the same thing will apply to gaming apps and the like before they are purchased...I'm sure others will comment soon.