Biggest difference that I have found is that rechargeables die suddenly compared to a normal Duracell. Don't seem to last as long either but probably worth it in the long run. They certainly seemed to have improved quite a lot over the years
Standard cells are nominally rated at 1.5v, whereas rechargeables are 1.2v, but for most applications they seem to be interchangeable.
Some devices will tell you not to use rechargeables.
I use rechargeables wherever I can, but the biggest pain is capacity, they don't last as long as consumables.
Not too much of a problem with a torch, you just keep a spare set in the charger ready for use, but a damned nuisance if you have to have your smoke alarms down, or your clocks off the wall every few weeks!
If you haven't already found it look in the base of your maglite you'll find a spare bulb.they are good torched built like the proverbial outhouse,i have three two pencil ones (2 AA batteries) and one that uses two "D" cells.When i was working in our car workshop i as manager issued everybody with a maglite (30 torches in total) and two rechargeable batteries each with 10 spare to be kept in my stores and used on a strict exchange basis (No batteries no swap),this saved us loads of money and my stores did the recharging.
I recently bought an LED torch with a rechargeable battery. The battery is a single unit but I suspect its 2 cells in an outer cover, and is charged in situ with a mains adapter. The torch has a 3 watt Cree LED 'Bulb' and is exceptionally bright. It actually has 2 brightness settings (plus a flashing one) and the paperwork reckons it will run for 68 hours on one charge, (probably on the lower setting). There also a torch from the same place with a 10w Cree LED. Can't imagine how powerful that one is.
If you do go for the rechargeable 'D' cells its worth considering the 'Good to Go' batteries which hold their charge for much longer. I've replaced most of my old ones with these.