Been using the Xtar 4150mWh AA's for about a month or so. I got the 8-pack+BC8 charger on Amazon. They do NOT work with high drain devices, but for 1A or less current draw they're pretty good, especially for devices, like you mention, that don't like the lower voltage of a NiMH.
I'm testing the Xtar 1.5v Lithium rechargeable 4150mWh head-to-head against Eneloop Pro 2400mAh NiMH in a 10 lumen solar garden light - unknown power draw. After 16 hours, the Eneloop is slightly dimmer than it started, the Xtar is still full brightness - at least to my eyes. At start of testing the light output was (at least visually) identical.
I'll also be setting up a test using a 3s-2p medium-drain flashlight on medium & low setting (1.5v Li-rechargeable will light high mode for about 2 minutes then starts to flash), but with only 1 flashlight, it will take quite a while to get results.
But now, I'm eying Ni-Zn rechargeables..... Stated specs:
> 1.6V nominal 1.85V fully charged
> 3000mWh claimed capacity (about 1,800mAh)
> No problem running high drain devices
> rapid charge
> keep steady output till drained
Don't know how true any of these specs are, but I've got the EBL charger + 8 AA battery set in my Amazon cart for payday... The high sustained output + ability to run high drain devices (even at reduced runtime) has definitely piqued my curiosity. BUT, the 1.85V full charge voltage could potentially be problematic for electronic devices...