So, it seems that new high end dual .... vps servers
will replace single chip low-mid dedicated servers in HD input/output performance.
In my opinion anybody with heavy mysql usage will benefit from it.
Now, get some more RAM for php operation and many vps servers will replace as i said low-mid end dedicated servers .
A VPS has more in common (performance wise) to a shared served than a dedicated.
Sure, a lightly loaded VPS will trounce a budget dedi (then again, so will a lightly loaded shared box if the hardware spec is substantial)
With a dedi, you are getting 100% of the power, 100% of the time.
Just see what happens when the other 10+VPS accounts on your box all start trying to access the hard drive at the same time...
A VPS is never going to replace a true dedicated machine, however much their abilities are touted.