Alan's record of support is one of the reasons why I went with both a DBS and a CL1H, and I'm confident in saying that a lot of the problems people have had with their Derees were self inflicted as others in this thread have mentioned (mostly backward battery installation). Still, Alan keeps "taking care of business" which continues to earn points from my perspective.
To the OP question: I bought both a 2SD module and a 2SM module with my DBS with the intent of using the 2SD most of the time, but having the 2SM on hand for when the house power goes down so I can use CR123's as backup.
I played with both of the modules at first just to, well, play, and they both worked right out of the gate as advertised.
Yes, my 2SD has a whine when in low setting (it's more like a "sizzling" sound, like bacon frying), but it's so quiet that I have to actually hold it against my ear to hear it. So no biggy for me.
But here's why I'm posting: Something I've come to find out on my own is that you should NOT screw the pill snugly into it's socket in the reflector.
Leave it loose at least a half a turn, or out to even a full turn.
Here's why: It's already mentioned somewhere that you can damage the electronics of the pill if the pill or barrel assemble is cranked tight. Just lightly snugging up the bezel to the reflector housing, and the reflector housing to the barrel, is all you need. The O-rings impart enough friction so that it won't come loose.
But there are two other reasons to leave the pill loose up to a turn when you install it into the reflector. You should notice that the pill will have a little "slop" due to the clearance between the threads. You should be able to wiggle the pill just a little because of those loose fitting threads.
Reason #1. The pill is an exact fit into the hole at the bottom of the housing that the reflector screws into. If you snug the pill tight, it will invariably be held off-center just a smidgeon; just enough so that the pill will bind when putting it back together and you'll find that the assembly won't screw together all the way unless you "crank" it tight which is one instance where you could damage the pill. (Note that I didn't force mine, but stopped to investigate why it wouldn't seat easily like I expected it to. So thankfully, I figured this out without having to ruin a pill).
Reason #2. If the pill is turned in almost all the way just short of snug so that the reflector assembly does screw together all the way like it should, you "may" find that the beam is a bit ringier than you like or is less than stellar in some other way.
This comes from the LED being at a less than optimum height with relation to the reflector. However, by leaving the pill loose about a half a turn or so, it changes the height of the LED to a better position.
So if you don't like the beam you get after changing out a pill, try loosening the pill a little to see if it changes things for the better.