The Android Market web client is already up and functioning as of right now and includes many great features. Users can see which devices they have connected to the Android Market and see which apps are installed on which devices. You can browse for apps by category or perform a search, just like in the app.
However, once you obtain search results, you can click on "Search Options" and sort the results by several ways, including by device compatibility, which is accomplished by selecting which Android device (that you own) you want to install the app onto. Once you've found the app you are looking for, you make a few clicks and the app is downloaded (and purchased, if it is a paid app) onto your phone and installed automatically.
Browsing for apps using the web client seems so much nicer on a big screen, as most of the relevant information is displayed in an easy to read manner. You also tweet about an app or rate it from links built into the web-page. Google contends that the site is a great way to manage your apps, and while it is a great way to install them, I wouldn't call it managing without the ability to uninstall apps from the phone, which the site does not have yet.
As I've mentioned before, Google is unhappy about how paid apps are selling, and it is easy to see in the web client, with paid apps often taking priority in the display results. In addition, the main pages of the web client all have a "Best Selling Games" area full of paid games."
The upcoming in-app payment system for Android was also announced at the event, which will be available to developers who integrate Google's in-app purchasing SDK into their apps. Expect the service to be functional sometime in before the end of Q1.
Google is also in the process of enabling "buyer currency support", which will allow developers to choose how the cost of an app is displayed to customers browsing the Android Market. Developers will be able to choose a specific price for supported currencies, or they can continue to use the current method. This ability will be rolling out in phases (expected to take around four months total), so it will take time for developers everywhere to use this feature.
Head on over and check out the site for yourself, if you haven't already.