Seedbox Discussions SATA 3 Hard disk

It would be great if someone had switched(or experimented) from sata 2 to sata 3 hard disk to post on their speeds and experience here. I wonder what is the speed difference in practice:)

I think sata 2 hard disk is faster than 15MB/sec cuz i'm pretty sure my shared seedbox can achieve way more speed than that.I think i have seen 30MB+/sec before.