I disagree. According to Wikipedia, it's been six years since EC2 launched. Since 2006-equivalent hardware is much cheaper in 2012 due to Moore's Law, (or alternatively the specs you can buy with a given number of dollars in 2012 is much better than it was in 2006), and since the original EC2 machines have probably been in service long enough to generate sufficient revenue to recover their upfront investment and make a profit, it wouldn't be unreasonable for Amazon to start retiring those old machines and use the better price/performance point of new hardware as a business justification to give customers some combination of price breaks and spec upgrades.
If you feel like Amazon should be cheaper overall due to Moore's law (and remember: they have lowered their prices numerous times since they launched on everything from hardware to bandwidth), then the price of the things we are comparing to would also be cheaper (as these are all just virtualized subsets of larger machines).
And I'm sympathetic to that argument where large amounts of disk are concerned... but I do wish we could have a small amount of ephemeral disk to be used for swap space.
Not because of a fault, but because they don't know instance disks are ephemeral.
Permanent storage as a default is a saner default as well.
As ephemeral disappears when you stop an instance (presumably, when the system is given the opportunity to relocate your instance to another machine), I've always suspected that ephemeral storage was part of local disks on the virtual host's chassis -- as opposed to a SAN or other kind of network-attached storage. As such, you probably end up with the same unpredictable performance you find in all virtualized resources, since it is very unlikely that Amazon is giving you your own storage.
Before benchmarking ephemeral storage you have to pre-warm it, which might have contributed to your findings. Ephemeral is worlds better than EBS, particularly in outage scenarios; if I could convince everybody on planet Earth to stop using EBS, it would be a noble cause.
Happy to be proven wrong but this is based on a year or so of experience dealing with EBS. You can't see the EBS traffic in your tools (at least that I've been able to find), which complicates things.
It's all kinds of different on VPC instances, therefore I suspect the network interface model -- and possibly EBS connectivity -- is different on those. So, who knows? I'd kill for Amazon to be more forthcoming here so I could understand the infrastructure running my fleet, but, I don't and they aren't.