It happens whenever I resize a layer (any type of image) or generally resize an image. It's always so much worse than Photoshop's quality. Very noticeable.

The problem with using an external tool is I often want to resize layers on the fly to fit them into a final image I'm working on. So using a third party tool to do that goes from a 5 second operation to 5 minutes because I first have to resize it in Gimp to get the dimensions and then resize it "for real" with a different program and then place that into the Gimp image.

It's gotten to the point now where I'm looking for an alternative to Gimp, or I'll just go back to using Photoshop full time (even though it's a huge waste of $ since I only edit about 2 images a week).