The previous HP EX-487 Windows Home Server was notable both because it was a good WHS, and because it had the ability to support Time Machine over the network on Macs. The EX490 and EX495 do even more.
One of the most important additions is the ability to do "bare metal recovery" on a Mac from Time Machine. This means you can completely restore your Mac from the network backup using the disc recovery utility that's bundled in. Also upgraded is the ability to do administration on a Mac.
There is also an included video conversion feature, which handles unprotected DVDs, as well as increased power (the 490 has a 2.2GHz Celeron and the 495 has a 2.5GHz Dual Core Pentium) and a "better" user interface. The ability to stream media from your iPhone or iPod Touch via a free app is included as well. And, of course, you get the standard Windows Home Server functions that we love using on a daily basis.
Preorders start today, but there's no solid word on a ship date.