James Dickens asks: Why not a server?
And it's an interesting question. Why, in a house with multiple computers, do you not have a dedicated machine somewhere and store all your files on it? It makes a lot more sense than having files spread at random amongst all those machines.
My own solution to this is a portable USB zip drive. I use this to carry stuff about between my machines, and between work and home if needed.
I'm not sure that the suggestion of using a real computer (and an Ultra 2 certainly qualified as a real computer) as the server though. Yes, I know that Solaris is an absolute doddle to administer (yes, really - once you've got to know it). But it's bad enough that everyone owning a Windows PC has to be a systems administrator, without expanding that even further. Even though it pays my wages, I'm a firm believer that when it comes to systems administration, less is definitely better.
Using a general-purpose computer doesn't necessarily make sense to me. (The one situation where it really comes into its own is if you were to use it as something like a Sun Ray Server.) But generally, some sort of appliance seems to make more sense.
And an appliance running a cut down OpenSolaris with ZFS would be a stunner.
The only downside to a server is that part of the assumption is that it's always on. I'm not sure that we should be encouraging that and the accompanying waste of power when there's so much damage already being done to the environment.
Hosted services - grid, if you like - also have limitations that are painful. They neatly solve the administration, availability, and backup problems, though. The biggest problem I see is that upload speeds on my internet connection are absolutely pathetic. Most internet connectivity is highly asymmetric - fast download, with just enough bandwidth the other way to handle the administrative packets and not a lot more. If we are to see hosted storage really become useful, then upload speeds are going to have to be significantly increased. (And, frankly, network reliability could stand a little improvement.)