"None" interpolation is occasionally useful as well, in image with really striking edges.
Agreed that the older downscaling algorithms aren't great. My impression is that they do a nice mathematical job of downscaling, but not a great perceptual one.
You just scale the image down and it looks flawless and takes like 2 seconds. In over 10 years of using Photoshop I never once noticed a blurry downscaled image, but the first time I used Gimp to resize an image I immediately saw a poor result. I used every resize strategy too (including NoHalo and LoHalo -- they are both really bad compared to Photoshop).
It makes working with Gimp for any web style graphics a huge hassle because down scaling images is something you do all the time, and it's not just the final image too. It's every layer you're working with. Having to export every layer into a third party app and then re-place it is a huge time sink.
convert -resize from ImageMagick is another option.
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).
I started using Gimp a few months ago after 10+ years of using Photoshop. My biggest complaint is the quality of scaling an image down. It's really really bad compared to Photoshop (even if you play with the low level details of picking the scale strategy). It always seems to come out blurry or fuzzy, to the point where I stopped using Gimp for that. Is there a better way to scale images?
Also, I just wanted to throw in a comment of, if you're switching to Gimp, don't immediately discount it for not having features you're used to with Photoshop.
For example, with Photoshop, if you copy an image to your clipboard outside of Photoshop, then you when you create a new image in Photoshop, the dimensions of the canvas will be set to the image in the clipboard. This way it's super easy to make a new image, paste the image from your clipboard and now you have a properly sized image.
Gimp has this feature but it's not implemented in a way that's the same as Photoshop. Instead, with Gimp you can just press CTRL + Shift + V to paste the image from the clipboard into a new image and it's all set up and good to go. The menu item is "paste as... new image".