I wold have a hard time estimating the amount of money I've saved by using these batteries. I've been using them for years in everything from remote controls and flashlights, to MP3 Players and digital cameras, all with great success.
I've charged, used, and recharged my supply of batteries several times over, with no major problems. In fact, out of all of these batteries that I've purchased through the years, I've only had two that seemed to fail prematurely. I'm not sure what was responsible for their failure, but the remainder of them are still going strong.
Do be aware when purchasing these, and note the rated capacity (i.e. the "mAH" number) of the batteries before you buy them. I have come across some stores that seemed to be clearing out their older stock of lower capacity batteries. Generally speaking, most people will be interested in the highest capacity they can find, because a higher capacity battery should power your device of choice, longer than a lower capacity battery. Higher capacity batteries can take longer to charge, though, so there is a minor trade-off.
When fully charged, these batteries will be approximately 1.4 volts, which is a little lower than a standard battery, so you may want to check your devices to make sure that they can handle a slight difference in voltage. Also please understand that these batteries will self-discharge far faster than normal alkaline batteries when they are just sitting on a shelf. So, while they make great "everyday use" batteries when you can recharge them regularly, you may not be able to depend on one of these batteries if it has been charged and stored unused for a while, especially in an emergency. Because of this, you may want to keep a small stock of normal batteries on hand for use in emergency situations.
Besides being more economical than normal batteries, these are also better for the environment because they can be reused hundreds of times. So, if the environment is a concern of yours, you can feel good about doing your part to cut down on excess waste, while you are saving money. Seems like a pretty good choice to me.