Originally posted by VoiceOfReason Sounds like it is a resounding no on getting a K3 for the trip. I don't seem to have the AF issues so many others do with the K5, but maybe because I am used to it. I was mainly wanting to see if the increase in resolution and sharpness is that much.
I'm going to hedge that a bit. While my K3 was in service, someone loaned me their K5IIs. Pentax buddies are awesome, or at least this one is. It was a good camera, but I was *so* relieved to get my baby back.
I felt there was a noticeable difference in IQ using the same lenses (for my style) and the K3 focuses on small objects much better. With the K5 I was constantly in MF to get things right. The increase in selectable AF points alone with the K3 was huge, for me. I also found the K3 easier to use, even given my familiarity with the K3. I used the K5 for a week, which was long enough to get used to it, I think. Moving from a K-x to a K3 took me about 20 minutes.
Now, if I owned the K5, I may not have upgraded. I certainly won't be replacing my body (barring disaster) for a few years. But I really do think the K3 is a sizeable step up. At least it is for what I do. I do a lot of photography in less than ideal conditions and lots and lots of macro shots. You had better believe 8 frames per second is a huge help when you are handholding trying to get a sharp ID photo of a plant and it's windy.
That said, if you are going to Europe to go on vacation and take snapshots -- don't buy anything new. Enjoy the trip and have fun taking photos. I don't own the 18-135, but from what I gather it's not the most amazing lens ever, it's just a solid walkabout lens.
However, if this is a photo excursion opportunity for you and you are packing filters and tripods and whatnot... the K3 costs less than most plane tickets, especially when you have a nice stable of lenses ready to go.