It was after watching the "Strobist Lighting Seminar" DVD's that I made the jump to rechargeable batteries for my flashes. Why, because only an idiot would listen to advice from David Hobby and then ignore it.
If I had to pick one thing I have not liked since making the move to rechargeables (and there only is one thing) it would be the fact they they drain rather quickly (and completely) when doing nothing other than sitting in your bag.
Since reading a couple of reviews this past week I am seriously considering making the move to the (relatively) new Sanyo Eneloop batteries.
What separates them from the rest of the herd of rechargeable NiMH batteries (addressing my problem) is that the Sanyo Eneloop's have "low self-discharge technology" (translation = they stay charged in your bag).
Just how low and slow is their self-discharge rate? This image pretty much says it all:
In a review done by Betsy Finn she tested standard NiMH batteries (2650mAh) against the Eneloop batteries (2000mAh) with the Eneloop batteries coming out on top in many ways including quicker recycle times.
Another was done by Stefan Vorkoetter, he tested Eneloop head to head against other low self-discharge batteries and the Eneloop's came out on top here too.
You can read more about Eneloop on the Sanyo website, you can also find the user manual here.