Having only just found this thread, I may be too late. But it's worth reading. I did a considerable amount of research before making my own decision. This is the conclusion I came to:
I'm not at all convinced by TimeCapsule. With only one drive, no fan and Apple's one year warranty, it's as much of a liability as it is a rip off. Expensive paperweight imo. It sure as hell isn't a viable back-up solution. Not even the Iomega 1TB jobs are as good as their advertising. But I do like the enclosures.
If one regards 50% redundancy as acceptable, then two server-grade HDDs in a RAID 1 or mirrored Array, employing a fan cooled FireWire enclosure is the minimum one should consider.
But this solution is only really viable if that too is covered by an off-site online back-up.
Real single unit back-up only begins with RAID 6 that offers Striping and Parity, where you can afford to lose two drives. And then you've still got the risk of theft and fire etc. Scary isn't it?
The other thing you need to bear in mind is that although Steve Jobs described TimeCapsules as having "server grade hard drives", Apple are only offering the usual 12 months guarantee. Why is this significant? Well, server grade hard drives or enterprise drives as they are described in the trade, leave the manufacturer with a five year guarantee!
Wireless back-up isn't exactly a foolproof option either. There are always security and stability issues to consider. All professional solutions use cables. You have the choice of USB, USB2, Firewire 400 and Firewire 800.
As a very sensible alternative, there's online storage. £150 will buy you a hefty amount of online storage. Google it and see what you can find.
Finally, remember you're dealing with a hard disk drive that's running all the time your Mac is. Yes it's vital you back up. But any advice you get from anyone who's only had one for two weeks, two months or even twelve months... isn't worth a great deal, other than to assess set-up issues, compatibility and early glitches. All hard disk drives have a finite life. There are no long term tests yet.
Yes this is good, a few people suggested buying an airport extreme and an external hard drive but they forget that although the time capsule has the inbuilt hard drive it can also accomplish this task aswell with an external hard drive making the possibilities endless!