I'm having similar problems to a poster before me, JTRocks.
I've had several recent problems, which I'll list for reference. Most recently, I had a strange confluence of problems including a cylinder misfire as well as check engine light and flashing HOLD light. It was diagnosed as partly an issue with bad relay as well as water inside the sparkplug/coilpack area. The tech (a KIA technician at a local dealership) was dumbfounded by the water issue and it took several attempts (costly tows each time) and he finally gave up and then coincidentally it hasn't happened again.
My current problem is that the automatic transmission will not shift out of first until near redline, or unless I "double tap" the gas pedal, and it is displaying the check engine symbol. I recently read about using the hold switch but hadn't thought to try that, since I was just concerned with getting the vehicle home (was less than 1 mile away when it happened). Within two days prior to this happening I had noticed that the engine was not shifting as "snappy" as usual, letting the rpm's climb far longer than normal.
I don't have a code reader or volt/ohm meter currently, and I'm not too confident about getting the vehicle anywhere under its own power. I'm not very auto savvy, but I can follow directions!

As I mentioned at the beginning, it sounds quite similar to JTRocks' post, except that my idle is normal (right around 1k sitting in park, neutral with brake, or in D with foot on the brake).
All fluids are fresh and full, the vehicle starts easily, idles fine (not as smooth as it once was but normal by all accounts) and I can manage to reverse down the driveway and then put it in Drive to get back to the top of the driveway.
My basic intuition tells me it's wiring or vacuum related since the problem is unlike the crazy shuddering/stalling/lurching I was getting in the past with the previous problems.
Any advice or suggestions would be greatly appreciated. My father is very good with automotive problems, but we don't have a book for this car so it's difficult to know what to look for, but if we can get steered in a general direction, I've no doubt we could tackle it, provided it's not a complete rebuild or something crazy!
Thanks in advance, and if I've left anything out please ask!
-Mark