Re: AA rechargeable batteries were always good value
>Aren't most rechargeable AA and AAA batteries 1.2V instead of the 1.5V from disposable batteries?
Yes, this can cause problems, there are various articles around the web, below is one I found from a quick search.
I actually found the big issue was that rechargeable AA's tended to be slightly larger than disposable so were either a tighter fit in the battery compartment or didn't fit it at all.
Given how long rechargeables have been around, I suspect very few gadgets designed in the last 15 years exhibit this problem. Certainly, I've not encountered any devices that won't work with rechargeables, including those the manufacturer say aren't suitable for rechargeables.
One thing I've noted more with rechargeables is with the flashgun (uses 4xAA). If I haven't used the flashgun for a while, with rechargeables, I can expect the first set to drain very quickly. However, with the disposables, because of the different discharge characteristics the first set seems to last longer, until you measure the flash cycle time and realise that it has grown longer. Additionally, with rechargeables, I get greater consistency of cycles - useful when taking pictures in rapid succession, before they quickly die.