1GB/s is a bit much for an SSD, since SATA currently only goes up to 6Gbit/s. PCIe-based SSDs can do it, but for a good SATA SSD, you can expect speeds ranging from 100MB/s to 500MB/s depending on the workload.

Most of the speed advantage SSDs have comes from having a dozen or more flash chips that are internally treated as something like a RAID array. Memory cards and USB sticks usually have only one or two chips.

It's quite significant. SD card is fine for the hacker community though. They have different intentions I suppose. SD cards weren't really designed for OS (particularly if you forget to disable a pagefile which will constantly write old memory to "disk" and drastically shorten its life)

To be fair, a class 10 SD card could be ten times faster than the figure you quoted. Still a big difference, of course, and I imagine there are some write queueing feature differences as well.

In theory. On the PandaBoard I max out a class10 card at 30 MB/sec.