My original 3DS which I bought after the first price drop could barely hold a charge.  I used some money from tax return to buy a New 3DS XL as an "excuse" to upgrade.  I knew I could replace the original 3DS's battery and eventually ordered one for 15 plus 5 for shipping off Nintendo's website.  It was pretty obvious it needed replaced considering it is bulging on both sides in the middle (I'll recycle at a battery store eventually).  So my original 3DS should be almost good as new and it was a pretty easy process that didn't cost that much money (had a small screwdriver which I used previously for upgrading my Wii U gamepad battery to the 2550mAh , they cost me a little over 2 dollars for a pair). 

I was just wondering if anyone out there had a 3DS battery go bad on them also?  For those that haven't do you notice a decrease in battery life?

Not for now, but I agree it doesn't last as much as it used to. I suppose by the time it needs to be changed, the handheld NX will have arrived, so the 3DS won't go out of my house anymore.

I've had mine since launch and I've had no issues with the battery so far.

No, still working.

Nope, still works.

Nope, I changed my 3DS after almost 4 years for different reasons but the battery was all right

Yup. 1 month ago I changed the battery in my black 3DS XL. Fortunately a new battery+screw driver cost me less than £5/$7 and so far it's working fine.

I bought this: http://www.ebay.com/itm/221653673024

Nope.

I feel like I buy a new model before it ever becomes an issue with my older one

No.. and I've used it for quite some time now

My DS has a longer time usage and didn't need to replace that one either so it's pretty good!