I also used the OS2AHCI community version at hobbes os2ahci_v0-1-4.zip (2011/09/16) and worked very good for me.
I couldn't get it to work for more than about a minute, without trapping, on either of my systems. The "official" version 1.22 works perfectly on my Lenovo ThinkPad T510 (even with hyperthreading enabled), and it takes about 4 hours on my Asus M3A78-EM motherboard, with quad core Phenom processor, before it traps (more analysis to do with that).
What would be a good test that can be done under eCS to show some results of the HDD performance to compare it with AHCI enabled not enabled.
I think you would need to be very careful about comparing numbers. If you write a test to specifically show the advantages of AHCI, I am sure that it could be made to look extremely fast. On the other hand, sequential I/O in a single thread, probably won't show any difference. If you read the docs, very few programs (if any) are written to take advantage of the features of AHCI, and it would be pure coincidence if two, or more, programs happened to do something together to make the advantages actually help. Repeating something like that would be impossible, and I doubt if a user would notice the difference, without using some very fine timing measurements. On the other hand, AHCI does open the door for more overlap in I/O processing, if somebody wants to take advantage of it and write I/O routines that can use it. Some very heavily I/O bound systems may see some speed increase, if multiple programs happen to overlap their I/O a lot. In most cases you will see very little difference, and file system cache will hide any difference anyway (it is so much faster).
IMO there are three reasons to use OS2AHCI:
1) To test it to make sure that it works in as many cases as possible (see 2).
2) To support those systems that do not have any other option (apparently, there are already a few of them).
3) So that you don't need to switch the BIOS every time you boot another system that does (or doesn't) use it.
In my case, I have Win7 on my Lenovo ThinkPad T510, and the machine arrived with AHCI enabled. I was able to switch to Compatibilty mode in the BIOS, and eCS worked fine (in this machine, it is one, or the other). WIn7 was not very happy about that, but it is possible to convince it to use the old IDE mode. Once I got eCS 2.1 installed, with AHCI (due to a bug in the installer, the AHCI driver is not installed, unless you install using AHCI), I got Win7 to work with AHCI again, and all is happiness.
On my Asus machine, I have WinXP, which knows nothing about AHCI. Apparently, you can find a driver to make it work, but that seems to be a lot of messing around, with no guarantee of success. The Asus BIOS can be left set to Compatibility, and it will switch to AHCI mode if the AHCI driver is loaded before the Dani driver. Since I get a trap, after a while, in AHCI mode, I have decided to use the Dani driver, and worry about AHCI when I find some time to test it. If I switch the BIOS to AHCI mode, the dani driver, and WinXP, won't work.
The bottom line is that using, or not using, the OS2AHCI driver depends on a lot of things (not the least of which is the BIOS support). In a "production" machine, you are probably safer to stay with the Dani driver, unless there is some reason not to. At this time, it would be good for as many people to try it as possible, just to shake out the bugs. Someday, there may not be an option, so it would be good to have AHCI working properly. You may also want to use it for convenience (see my T510 scenario, above). The last consideration, IMO, would be whether it is faster, or not.