If you put in the batteries that came with the unit and they were alkaline, there was no manual to tell you to use high-amperage rechargables, and you therefore kept using fresh alkaline batteries and it kept crashing on you-- and that is what it's doing when it runs low on power-- you'd assume the system has some sort of issue with power management. The alkalines may no longer be included, but lots of people still think "What the fuck" when they put in their own AAs and they don't work properly, or the machine dies in 15 minutes.
Honestly, anyway you look at it, this is a fault in the GP2X's design. The GP32 had very similar hardware but would run happily on Alkaline cells. At the very least, a slip of paper in the box that says you MUST use high-current NiMH cells or Lithium Disposable batteries, and the same notice on the box, is a crucial measure.
The note of 'lots and lots' of rechargables made sense too. Most rechargable cells are NiMHs well under 1000mAH and last about as long as alkaline batteries do in most devices. Unless you buy the >2000mAH cells that are fairly specialized you will get shit performance with 'rechargable batteries'. Again, the buyer needs to be educated.
Secondary example from my everyday life; yesterday I bought a multimeter at Radio Shack. It didn't work. I had to dig around INSIDE THE PACKAGE for somewhere it said in TINY PRINT it needed a PRIOPRIETARY 12V BATTERY. I had to unscrew the back of the device to even install the thing, if I bought it, too. That probably voids my warranty. No mention was made on the package that it didn't come with a battery, and no requirements for the spec of battery were listed which leads a rational buyer to believe it comes with an internal cell that is meant to last for years, like a watch battery usually does. Not the case .. and I was, and still am, pissed off. I have to drive back and return the whole mess tomorrow or buy this special ridiculous battery. I imagine this is how a lot of GP2X buyers feel.