I am using shared to start up my site but am switching to VPS right as I open it(strange I know) mostly because the kind of traffic my site will bring will require root access.
Have you looked at options like RackSpaceCloud.com?
While you'll have to be somewhat hands on from the beginning, their CloudServers option will start you off at $11/month for run-time and usage would be variable. You can add/remove nodes as necessary to support your needs.
They've been good to me for a few Apps that I've had to deploy. Not the best choice for running and administering a website with much easier choices out there. I do know of people that have their CloudServers configured with cPanel or people that use it to mirror their other servers.
I believe it is a little too simplistic to say shared is ___, vps is ___, and dedicated is ___. There is a lot more too it, except for the basic obvious stuff such as root & ssh access.
Usually the people behind the service is one of the key components.
Exactly, I'll take a VPS (virtual machine) with a Nehalem processor and 6 GB of DDR3 over a dedicated server with dual Xeons and 8 GB of DDR2 any day. Dedicated does not necessarily mean better or faster, but it almost always means more expensive.
http://www.limestonenetworks.com/ It is decently cheap...about as cheap a dedi you will find that still maintains great quality . What is the stuff team? lol?