SureFire appears to have finally found a rechargeable 123A form-factor battery that they're happy enough with to put their name on it. The batteries are $6 each, and are available in two-packs as well as a combo with a charger that works from the wall and from vehicle (12V) power supplies. From the product shot it looks like they're using K2 Energy's LFP123A, which uses lithium-phosphate technology.
SureFire's traditional lithium batteries, which typically sell for around $2 each, will last about twice as long as a fully-charged rechargeable—but SureFire notes that the maximum output levels should not be different between battery types. K2 asserts that their batteries are good for over 2,000 charge cycles (SureFire more modestly claims only "hundreds") but they don't provide any details on their performance characteristics as they age.
The big challenge for rechargeable 123A-style batteries is that they typically operate at ~4.2V, whereas the lithium versions produce only 3V. This can have the nasty effect of overpowering and damaging some electronics and incandescent flashlights that are only expecting 3V cells. It looks like these batteries haven't solved that problem, as SureFire has a disclaimer not to use these cells with incandescent lights.
As rechargeable AA and AAA batteries have improved dramatically over the recent years—witness the fantastic eneloop batteries from Sanyo—rechargeable 123A batteries have been hobbled by the high voltage problem. This, in turn, has lead to a lot of people turning away from 123A-powered devices in favor of ones that use AA or AAA cells. I'm glad to see a big name step up and support a rechargeable 123A form-factor battery, even though it appears they haven't addressed the high voltage issue. And, though their runtime is a bit anemic, the ability to recharge them makes them a good value if you 123A-powered devices frequently. They're also invaluable in situations like large-scale disasters where normal supplies aren't easy to obtain but recharging existing cells from portable generators is possible.