The likely bench seq read throughput on my Mom's system is probably around 300 MB/s, with an Elm Crest SATA-III connected to an SATA-II controller. The jump from HDD to SSD in that system was quite noticeable.
I could tell that my ISRT configuration was faster than the Elm Crest rig. It would bench somewhere around 400 in sequential reads.
Once you're configured for greater performance at around 500+/-, you notice less and less of a difference. But there are some things I noticed as faster with the RAPID configuration.
The entire thing about these caching schemes that indeed improve performance: they must be stable. As long as your RAM is good, as long as the Samsung SSD is good, it appears that RAPID is stable -- assuming your SATA configuration isn't buggy or you don't have a driver problem.