It might depend on the controller. I used to have an Lenovo Thinkpad x121e. I needed to switch the SATA Controller to compatible mode as in ahci mode no drive was found using ArcaOS 5.04 (i do not have this Laptop anymore so i couldn't test with more recent versions.)
On my motherboard, which is a AMD 890FX and SB850 chipset, I couldn't get the AHCI driver to work reliably. It would find the SSD, no problem there, it would access it just fine...however periodically the machine would literally freeze...no response, everything stopped, this would last for about 5-10 secs, after which time it would then proceed to run once again.
I tried to narrow this down to either my JFS cache settings, or driver parameters, heck, even played with the motherboard ports I was connecting to...never established the root cause, so I gave up on trying to get AHCI working here.
As to the speed comment...I'm not sure that it's any faster actually. The testing I was able to do showed exactly the same results, however, I will say that the system 'response' seems to be improved, and that's precisely what AHCI can deliver, after all it re-arranges the drive commands in such a way that the hardware itself delivers the information faster. This is normally very pronounced when dealing with spinning disks since the amount of head movement is minimized, and that in turn allows for a more efficient retrieval of data from the disk. SSDs on the other hand don't seem to benefit from this as much, at least that was my experience while I was playing around with it.
Bottom line: you need to test your hardware, and if you are running AOS and encountering problems do report this to AN by logging an Issue, it's the only way to improve the software by making the authors aware of the issue.
