Our IO flavor has 2x 1.6TB PCIe flash cards, this is how we see most users running databases or otherwise persisting "hot" data. I've gotten to play with these over the last few months, and its really incredible how fast they are - they totally crush even high end SSDs. People have traditionally used these in a tiered setup to accelerate spinning disks, but the costs have come down to where it hardly makes sense to use anything else for low latency persistent storage.
We're working to hook this up to our existing block storage offering as well, which will offer more flexibility to attach SSD or spinning disk backed block devices to any flavor.
Reliability is similar to an SSD. The underlying storage tech is basically the same: some flash chips, with a controller that handles wear leveling and so on. Just that instead of running operations through a SATA controller it uses the PCIe bus, which offers higher bandwidth and lower latency.
Interestingly, Apple is shipping PCIe flash in all (I think) of their latest laptops.
We're working to hook this up to our existing block storage offering as well, which will offer more flexibility to attach SSD or spinning disk backed block devices to any flavor.