If you aren't a huge Windows Media Center fan there are alternatives. Also if you don't have a copy of Windows 7 you can always go the Linux route.
Xbox Media Center basically works on any operating system out there. If you don't want Live TV and just have a lot of content this might be the route to go. Lifehacker has a great guide of installing XBMC and Linux on a revo:
People love Boxee and it has a lot of great features. It is built off XBMC and offers a lot of streaming content and will organize you content as well. No Live TV here either, but again Lifehacker has a great guide of installing it with Linux:
Aspire Revo Alternatives:
Zotac MAG with Intel Atom N330:
The Zotac MAG is basically an AR3610 but with no operating system installed. It comes with 2GB RAM, 160GB hard drive, eSata, Vesa mount, and much more. If you have a copy of Windows 7 this might be a good alternative for you.
The Foxconn Ion barebone system is nice if you want to add a custom amount of RAM as it comes with none, and your own operating system. Priced at $270 on newegg.com it is relatively affordable and is comparable to the AR3610 after you put in your own RAM.
ASRock Ion HTPC:
The ASRock Ion HTPCs are a nice alternative to the Revo as they come in many different configurations and allow you to customize them a bit more. Most of them feature the Atom 330 with the ION, however they are a bit more expensive then the Revo.
Roku offers a Netflix, MLB.tv, Amazon, Pandora, and much more. It doesn't offer the same features as a full blown HTPC, but is a great alternative. It is relatively affordable, has great features, and great reviews. Take a look and click the banner to help support RevoHTPC.com
If you have more suggestions add them in the comments.