I went to the quarry a few times with the intention of photographing the Oxycheq backup light with some other lights for comparison. Unfortunately it never panned out, the vis has been horrible, and one day the vis was good but the camera batteries died right as we were setting the lights up. Here's my feelings on the light.
The construction is very solid, it's a very well made light. The aluminum is thick in the right places, the LED module is fully potted and permanently attached, it's a very confidence inspiring light - just what you want for a backup. The size is perfect. It's comfortable to hold on with your hand, but small enough to tuck them away on your shoulder straps and not notice they are there.
I'm not a big fan of the power switch. Its a rotating collar, with no detents. The collar is right around where the innertube on my harness holds onto the light. I don't like the odds of it rotating slighty (all it takes is 1/3 turn or so), and the light will go on. It is a sealed switch, but I think they should have added detents.
On both of my lights, the finish has some runs. The lights are anodized, it may have been a run with the dye (though they look like natural finish to me), not sure, it's only an aesthetic issue. For the money they cost, a perfect finish would have been nice however.
The holes where I tied the snaps on look like they were chamfered by hand after they were drilled to knock off the sharp edge so the cave line wasn't cut, but it did get cut and the snap fell off after a few dives. I don't think I overtightened the knot, but it could have been my fault. Either way I'm going to smooth it out a bit more so I don't risk losing a light.
I think the lithium CR123 is the perfect battery for a backup. Has a 10 year shelf life, they are small yet very energy-dense. You can buy them online for cheap - under $1 each now, and you can find them at most stores. The voltage curve is very flat, and they function well throughout a variety of temperatures. The battery life is nice, rated at 2.0 hours/full, 3 more with decreasing output. I have used them on and off on a number of dives, only gone through one change when they were getting dim, I can't give an accurate estimate of how long I used them for, but I was happy with the battery life. Unless I was doing long cave dives (I'm not), I would think it's more than sufficient for a backup, and if I were using it as a primary on vacation, I would have no problems either. CR123s are cheap and small enough, so theres no issue with changing them every few dives.
As far as light output equalling a 10w HID, I've used it next to both a 10w welch-allyn non-focusable (dive rite hand held), and a 10w brightstar (sea-elite aka salvo canister) non-focusable. Both HIDs were focused significantly tighter, and the hot-spots were significantly brighter than that of the Oxycheq. Because the hot spots are focused differently, it is hard to make a statement about brightness, but my gut feeling was that the HIDs had overall significantly more light output. Because of the wide beam, the range for signalling is very short. A buddys old-school (non led) scout was much better for signalling, as it's focused very tight. Overall light output was not even close though, the Oxycheq throws far more light than the scout, but not as far.
The Oxycheq backups won't replace a canister 10w HID, or even a handheld HID for a primary IMO, but thats not really their purpose. As far as I'm concerned, LED + Lithium is the perfect combo for a backup light, and the Oxycheqs are the best ones I've seen.
I also purchased a couple OMS aluminum backups. Next to the Oxycheqs, these things seem very cheaply made. Thinner walls, and the spring mechanism that holds the batteries is just goofy. There is a spring on either side of the batteries, and not a whole lot of tension. So if you shake the light, it will go on. If the springs are stretched too much or too little, the light won't turn on. I can't imagine what the OMS engineers were thinking.
If I were buying them again, I'd also consider the Salvo Rat. The Rat Jr. looks a bit smaller than the Oxycheq (maybe too small) and has only a 2w LED, while the Rat is 3xC so it's quite a bit larger than the Oxycheq (it looks like). But if it had a nice focused beam, it could be nice.
One of these days I'm going to hook the Oxycheqs up to a multimeter and figure out how much draw those LEDs are taking.
Rob