Yeah hmm. Sounds too sketchy, I'm going to file it under forget about it. It concerns me that it has additional connections, which seem like additional points of failure to me. You definitely wouldn't want to turn off power to a drive while the system is running, and you can't really "safely remove" internal drives to make it safe to power them off.
The drives that you will always have on, I'd just wire them directly and not through the switch. And then have the ones you occasionally use going through the switch. It should be ok - keep in mind I know nothing about it, so don't let my paranoia ruin it for you.
You're right about one thing of course. A drive can't be turned off mid-session. That's no great problem, though. I take your point about wiring two of the drives directly, but as I'll explain, that will involve more unsightly wires that I hate! (I'm used to motorbike wiring harnesses and converting faired bikes to un-faired...the wiring is grotesque unless you minimise it and hide it where you can)
In terms of additional connections, I'd beg to differ. For four drives running permanently, there are four SATA power connections from the PSU, with most power supplies this will come from one socket on the PSU. Then there are four SATA connections from each HDD to the mobo. With this system, there are two molex power supply connectors running from one of the peripheral PSU outlets and the four SATA cables from the unit to the mobo, so six in total and not eight. The other advantage that I had when installing this was that I did not have to use all of the modular power outlets from the PSU and this cut down on the wiring inside the case which improves airflow etc, because I limited the number of molex to four which was supplied by one PSU cable.
I am now running the system and it works so far (fingers crossed). The big test will be how reliable it is in the long run, but to be fair, the hardware is pretty simple and well made, so I can only hope that it is robust. We'll see. All I can say so far is what I have observed. The device is an Orico HD-PW4101 and it fitted perfectly into the 3.5" floppy bay, which is more than I can say for Akasa's FC-Trio fan controller: I had to slot out the 5.5" bay with a drill to fit that! The only negative comments I saw on the web about the HDD controller were about the stiffness of the wires on the SATA power outputs. I would agree with this. I cut off the heat-shrink sleeving to make these more pliable and made sure that the cables didn't cause a problem by tie-wrapping them to a handy drilled lug on the back of the unit. I wasn't happy with the length and rigidity of the rest of the SATA wiring loom either, but I don't like the ridiculous length of cables that anyone supplies with their kit!
Despite my shiny new rig looking good through the window, I am still grumpy. I know that the hidden side panels where extra side fans (that I don't even need) would go is untidy if you remove the panel. I am seriously considering making my own cables! That's what a fussy s** I can be.
Let's wait and see what reliability is like. If it goes up in a puff of smoke, I'll let you know and you can smirk knowingly!
Maybe I'll post a pic of the end result when I'm happy with it.