I've been testing the new Adobe Lightroom Public Beta 3 on a new Intel MacBook Pro and am impressed with the application's performance. There are also many UI refinements from Beta 2, including a new module: Web.
That's where I started experimenting. The Web templates are quite attractive, although you don't have much flexibility with them yet. There are 3 presets -- HTML gallery, Exif metadata, and Flash gallery. You have two options for exporting: Save to your hard drive or upload to your web server. You can enter your FTP settings directly in Lightroom saving you a couple steps.
The Develop module also received some attention. You now have additional tools above the filmstrip -- most notably a Before/After view, which is really handy while image editing. There are RGB value readouts too.
A member from The Digital Story community, Jeremey Barrett, has published first impressions of Beta 3 on his weblog. You might want to take a look.
One final note: still no official word on the Windows version yet. For now, the beta is only Mac. But you can sign up to be notified as soon as the Windows beta is ready.