Apple's Time Capsule sounds nearly perfect.

I think it's the sleeper product announcement at MacWorld, the thing that might turn out to be just as hot as the thin laptop.

Everyone with multple computers wants, or should be seeking, a super simple system that constantly backs up all the data on their home machines.

That's the promise of Time Capsule, but it's missing a crucial feature -- mirrored hard drives, to protect against the inevitable disk failure.

Hard-drives -- even the "server grade" ones that Apple says it's using in Time Capsule -- might last five years if you're lucky. That's why its safer to store things on a system with multiple drives that make copies of each other, in case one of the disks fails.

I guess you could periodically backup Time Capsule using external hard-drives, but that's not a very elegant solution and it's probably too much of a hassle for most people.

Mirrored drives are common now on PCs and external storage devices, so it seems like a strange choice that Apple made. Maybe it was trying to keep the cost low, so it could undercut the Windows Home Server products that it's challenging.

Windows Home Server is a nice solution and it has an innovative system that mirrors data on multiple hard drives, as many as you want to plug into the system. It also offers online access to files.

But Windows Home Server is much more expensive, especially to window shoppers at big box stores comparing it with Time Capsule. Hewlett-Packard's 500 gig model is around $600 vs. $299 for the 500-gig Time Capsule. HP's 1 terabyte model is around $800 vs. the 1 TB Time Capsule's $499.

A better comparison with Time Capsule would be the single-drive external backup drives, such as the Western Digital and Seagate models that cost a bit less per gigabyte. Apple trounces them by adding touchless backup and wireless features.

Ideally, Time Capsule will push Windows Home Server manufacturers to bring their prices down and add nifty wireless features such as the 802.11n hub that Apple included.

The pressure will really be on after someone writes an application that automatically backs up Windows files onto a Time Capsule (right now it works with PCs as a wireless external hard drive; you need the Macs' Time Machine backup software to use it for automatic backups).

Maybe by then, Apple will add mirrored drives and we'll have the best of both worlds.