If you have upgraded your Linode, what did you run out of?
For those who have upgraded to a higher plan, what was the constraining factor? CPU, RAM, disk space, disk speed, transfer or bandwidth?
I am using lighttpd and cgi (with C code) where possible instead of Apache and php (except for PunBB, which I hope will also be lighter than phpBB).
So I'm hoping not to run out of RAM that soon. It'll be fun to see how far I can stretch the Linode 360.
You didn't mention your traffic or where you've previously run this system, but since you're optimizing your platform to a high degree, I think you'll do well. I personally favor the Linode 1080 size; the 360s are for testing or things that can run more slowly.
If you don't want to jump to the next Linode size, you could always buy a bit more RAM under the Extras section of the Linode Manager (but upgrading is so much better--and cheaper overall).
Please let us know how it goes!