I've tried the Web-based player on both a Windows PC and a Mac, and it works and looks the same on both and worked without a hitch.
The bottom line
If you have a music collection and want to share it among multiple devices, and would like Web-based access as well, then you want Google Music. It's simple to set up and use, integrates well into Android and is easy to use on the Web. It's superior to Amazon's rival service because it lets you have a larger collection and because it handles WMA files.
For now, Google Music is free because it's in beta, and it's one of the best deals you'll find. It's not clear what the pricing will be in the future or if it will remain free. But after my initial look, even if Google started charging for it, I'd most likley be a customer, depending (of course) on the price.
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