[rentzsch]

I agree with your analysis, and that doesn't even include the value of your time.

However Time Capsules run hot and have a nasty habit of burning out every two years or so. I presume the Pi + external drive would run cooler and have a much longer life.

[Samuel_Michon]

Yup. I bought the original 500GB Time Capsule, the power supply died after 18 months. Apple replaced my Time Capsule for free. This one has been working fine since November of 2009, but I'll never trust it to be my only way of performing backups.

Time Capsule Memorial Register: http://timecapsuledead.org/

Time Capsule is a very convenient way to use Time Machine, and it works great until it dies. Judging from the other comments, that's the difference with the Raspberry solution, which apparently isn't very reliable and doesn't allow for HFS+ with Journaling.

[solarexplorer]

As already stated, the problem is that netatalk has trouble keeping the AFP protocol up to date. On the Linux box it doesn't make sense to use HFS since Ext3 is much more stable and also supports journaling...