> setting the size of pencil is completely unintuitive - I usually click in what appears to be input field, only to discover it is not (but instead some meter that sets size to some huge number)

It actually is an input field, but it can be interacted with in 3 ways. Clicking on the value focuses it, and allows editing by keyboard. Clicking and dragging in the bottom half of the block allows you to increase or decrease the value by dragging left or right, and the movements you make translate to relatively smaller value changes, so you can be relatively precise. Clicking and dragging in the top half of the block allows you to select a specific value by dragging, and the position of the cursor translates directly to the position of that value on the bar.

> sometimes when I start it it doesn't display toolbox

Agreed. It's hard to imagine a scenario when you open a file in GIMP and don't want the tools. While there may be some such scenarios, it's hard to believe that it's a common case.

> when I open the toolbox it is (sometimes) a vertical line of buttons (single column) instead of 5 columns that I begged it countless times to be

Oh, yeah. Having the toolbox form factor changing and the tool buttons moving around (seemingly at random) is by far the most annoying part of GIMP for me. I don't actually much care what layout is chosen; I just want it to stay the same.

The formatting you chose forced me to have to drag a scrollbar to the right to read your comment...

please no :(

> Floating point pixel values should be supported as of GIMP 2.10, though.

True! I have just updated to 2.10 and it can open floating-point tiffs of one or three channels. The support is very limited, though. It seems to ignore negative values or values higher than 1, so it is mostly useless to me. Yet, I'm very happy to see new advances!

Thanks! There's plenty of software that supports these features (and does not require you to touch any--gasp--java). I am just sad that these basic things are not readily available in GIMP, which could otherwise attempt to be a sort of generic tool for image processing. They seem to be focused too much in color photography, while the tool is not directly useful to people working with images that are not of this kind (e.g., astronomical images, microscopy, satellite, radar, and mathematical image processing).

Radar images (e.g., those publicly available from the Sentinel 1 satellite) typically come as complex-valued images. You look at the norm of the complex numbers to understand the structures, but for interferometry you need the phase also.

If you compute the Fourier transform of a scalar-valued image, you obtain a complex-valued image. It would be nice to be able to process these transforms with gimp (e.g., to "paint" a few parts in black to set those frequencies to zero, thereby defining a band-pass filter).

> GIMP's IWarp workflow is horrendous.

Welcome to 2018 where GIMP 2.10 is available and features the Warp Transform tool that does the same (actually, more) and works directly on the canvas.

My point exactly!

GIMP is GNU's image manipulation program, not photo manipulation program. Most images are not photos.