Rather than clustering, I'd rather see something more like VMWare ESX's migration of guest host/OS images among devices (v-motion). Run my common tasks in a guest host VM that is light weight, but does the general user stuff (web, email, IM, notes, etc.).

When I'm at my desktop at home, and I need to hit the road, I v-motion that guest over to my phone. If I need to check something while mobile, can do the basics on my phone. If I get to a coffee shop (or a meeting, or a library, etc.), I take out my netbook, and v-motion the guest over to the netbook. When I'm ready to get on the road again, v-motion it back to my phone. When I get to the office, I v-motion it from my phone over to my workstation.

And if the "VMware Player" type infrastructure that makes this possible decouples the display from the compute engine, then maybe you could also (while sitting at your workstation) fire up a heavier weight task, and it would immediately v-motion the CPU/RAM/etc. over to a big compute farm, transparently hiding that from you (ie. you keep using your workstation's display/keyboard/mouse without any changes, except maybe a slight flicker when the v-motion happens).

Of course, that requires a UI that will scale from the phone up to the workstation. Or a UI infrastructure that can instantly morph from a phone sized UI to a workstation sized UI (imagine for a second, ignoring the CPU architecture, the same application -- not two separate copies, but the _same_ application, running on both an iPhone and a Mac, but having an iPhone UI on the iPhone, and a Mac UI on the Mac -- you can actually almost do that with Cocoa, but I don't know that anyone has really pushed that possibility very far), so that your applications don't miss a beat when you v-motion from desktop to phone, but they do instantly take on the UI of the new environment.

But, without that, you'd either have to get used to a tiny desktop on your phone, or a giant palmtop on your desk. Or something in between (that wont be very good in either environment). Though, the new Sharp device being talked about over in the Competitors forum has what looks like a mostly typical Ubuntu environment (with one of the NBR launchers) running on a 5" screen. If they fix the bug about easily moving back and forth from conventional Ubuntu to NBR ... then maybe that would be the type of glue it would take.