I ran the performance benchmarks in the Samsung Magician software. They are:
Sequential read: 142 MB/s
Sequential write: 136 MB/s
Random read: 16,157 IOPS
Random write: 15,053 IOPS
This is after I used the "Performance Optimization" (which didn't really do much for these speeds). "OS Optimization" is set to Maximum Reliability. This does things like disable hibernation to prevent the creation of hyberfile.sys (to prevent excessive writes to the SSD) and disable search indexing (which requires a large number of random writes).
This computer uses SATA, but it's from 2005 or 2006, so it likely uses SATA 1, which is limited to 1.5 Gbits/s, or 150 MB/s. I imagine that the physical architecture of this laptop is preventing faster data transfer speeds.