1. It's impossible to write over files it uses (loaded textures, and models)
Yes, and yes, that's one of the little quirks.
Close it, and start it up again, if you need to modify stuff on the fly. You should not be using it to view textures with anyhow.
IIRC, older versions didn't have this problem, so you might want an older version if you want to use it that way.
2. it does not show reflectivity properly.
Actually, it's accurate, the shader's the same. The issue is the skybox, and the light's fullbright white, whereas the ambient is black. You can replace the skybox with something better, but you can't do anything about the ambient, which sucks.
3. it blurs my textures when looked at from a certain angle
That's an interaction between your drivers and the rendering environment. You're seeing mips, which are built during runtime if you use anything but DDS (this happens in Spring, too, btw, which is why using anything but DDS is not optimal).
If you use DDS, you won't have that problem.
4. it let's thing shine through it, so when I have upspring open I see some photoshop menus.
That's odd. Sounds like a driver issue to me. I don't have that issue.
5. it crashes sometimes
I've never had a crash, when using it's primary suite (resizing, rigging, rebuilding the surface normals, assigning textures). I can see that happening, if you try to use the animation stuff, it's not really finished, and jcnossen's never going to finish it.
6. it's not possible to load things by double clicking on them, you have to open upspring, click load... and search for it.
Yes, that's irritating.
7.it has all kinds of buttons but only 10/50 of them are usefull.
Er... other than the animation stuff, I use practically everything...
8. if you save something and select s3o or something, you also need to add the extention in the name (unlike other programs)
Yes, that's very irritating, and I asked jcnossen to fix it at one point...
9. It shows the textures with top-down inverted (at least on s3o with .tga)
It's designed to use DDS.
As is Spring, btw. I've read through the source about that fairly recently, and Spring natively handles DXT1 DXT3 and DXT5, as well as 8888, all correctly. The only problem is that you lose some fidelity of color, and will see some noise, if you use DXT formats. I've done some research on that, and if you reduce noise levels, you can greatly improve the compression results. That said, for P.U.R.E., I just use 8888, which is huge but is 100% accurate on all mip levels. It compresses at about 5:1, so the final result isn't a lot larger, download-wise, than PNG... and, since the mipmaps are pre-computed, your game starts up faster.
Pre-computing mip levels speeds up startup times for your games, and if you use DXT formats, you can
greatly improve the texture memory footprint. BTW, ATi's Compressionator is a very, very useful tool for making DDS with, if you have noise / color issues, and want to see where the compression artifacts are. I generally use nVidia's Photoshop plugin to make initial DDS with, though.
10. It forgets which texture was used by which s3o, I have to remember by heart which pair of texture is used by which model, and have reload both texture everytime. (Actually, it's more that it can't find the texture because it uses a wrong path.)
This is a problem caused by not setting the path at the start of a session. Click Settings-->Set Spring Texture Directory... and feed it the full path to your textures. I show full paths in Windows, so I just open the unitextures folder, copy-paste, and voila.
It should have had the path assigned to ../unittextures/ by default, but it's just set to the root. If you're working on putting a bunch of models together, you can just pile them in with the models, set them up, save them, then move them to unittextures.
