Chrome OS vs Ubuntu Netbook Remix
Although Chrome OS is based on Ubuntu, Google has no intention right now of targeting the mass market.
Instead, Chrome OS will be certified to run on specific hardware, which at the very least will need either an x86 or ARM CPU and a solid-state drive (SSD) for storage.
Most SSDs are faster than hard drives, which enables Google to squeeze the boot time as low as possible. SSDs are also much more expensive, but that's mitigated by the fact that Chrome OS is designed to operate in as little storage space as possible – we think you might be able to buy a Chrome OS netbook with just 1GB of storage.
As a respin of its standard desktop distro, Ubuntu Netbook Remix (UNR) is fairly hardware agnostic – it prefers to have an Atom CPU and an SSD, but neither of those are required.
In fact, largely thanks to the appeal of the Ubuntu brand name, UNR has probably received more widespread testing than any other netbook distro and so works well on virtually everything out there. There are even special versions of UNR available for Dell Mini netbooks, but generally you can run it on whatever you like.