Let me tell you my experiences with rechargeable batteries on the K200. Please sit back because this is going to be a little long.
After the amazing bundled Energizer lithiums I used two sets of Energizer 2500 mAh, which I will call "set A" and set "B". A was made in China and B in Japan. By the way, my charger is a LaCrosse BC700 (or RS700, as it's called in some countries).
Set A was not totally bad: after a full charge I managed to get 150-200 shoots. The problem was, when I picked up the camera after a few days it won't even turn on! And this even though the batteries were still displayed at 100% the previous time. Now, I know about self-discharge, but I thought it occurred over months, not days!
Set B was much worse. In fact, I never got a single shoot out of it. The self-discharge was extremely fast, i.e. the day right after a full charge the camera won't turn on. You can easily imagine how useless this set was as a backup. After it let me down two times in a row, I switched it to the "hopeless" drawer. This pack must be a defective one, as it has an extremely poor performance even on a low-drain device such as my portable CD player. I can barely get 10 hours of playing while any two batteries from set A run well over 50 hours. I tested set B in my compact Sony DSC-S60 camera. I charged it and waited for three days. Then I took a shoot (with flash burst) and the battery meter immediately dropped from 100% to 50%. That was the last straw: I shall never be buying Energizer rechargeables again.
I am currently using four Varta Ready2Use LSD batteries. Two came straight from the pack, while I had been using the other two for a few weeks in the DSC-S60. I made about 200 shoots with them and the battery meter is still at 100%. Please note that about 50% of the shoots were taken with long exposure times (30 seconds to 2 minutes and over) so this is already a good performance, considered that none of the batteries was at full charge.
This week I'm buying a set of Duracell Pre-Charged, which I am told are nothing but re-branded Eneloops. I certainly hope this is correct, as here in Italy Sanyo Eneloops are really hard to find in stores and expensive to get online. The fact that Duracells are Eneloops with a different label is stated by knowledgeable people on many Italian forums, and also on the influential
Candle Power Forum, so I can reasonably assume it's true. Someone even goes as far as calling them "Duraloops". More will follow in this thread.
A final note: at the end of August I'm going to Scotland for ten days: I'll be bringing two sets of rechargeable batteries (still don't know which brand) but I will rely mainly on a fresh pack of Energizer Lithiums.