Like one of my co-workers always said :
"cheap thing no good,
good thing no cheap"
Invest in a couple of sets of good rechargeable AA's,
(not Wal-Mart's Energizer or Duracell Ni-MH specials with a cheap charger)
and your K-x will perform just as well as if it had a dedicated camera type battery.
I picked up a few sets of Ansmann AA's from the local camera shop
after using Energizers in my camera for the first few weeks
ANSMANN AG: Batteries & battery packs
expensive at 30$ for 4 x AA's, double the price of Energizer Ni-MH AA's
but more importantly they keep their charge perhaps 3+ times longer in my K-x
The
ONLY reason I initially chose the Pentax K-x over other entry level Canikons
was that it used AA's!