Mac laptops work just like that. When you close the lid, they write everything out to disk and then go into standby mode. If you reopen the lid, they're ready to use in a second or so. If the power dies, then it'll restore from disk when the power comes back. They don't seem to do the checksum trick on preserved RAM; I suspect that Intel's RAM controllers don't support it.

The downside is that writing 2-4 GB of RAM out to disk takes time, and it's uninterruptable. So, if you close you lid and then realize that you forgot something, it'll be 20+ seconds before you can get access to your computer again, and possibly much longer.