Does anyone use 3Dconnexion devices for playing games? I do and I'm having a bit of a compatibility issue.

First of all, use a SpaceMouse Compact, and I know that it's working because it works flawlessly in the 3D modeling demo included with it, and it also works decently well in a few games (exceptionally well in the Overload demo - I really need to get that game!), and it even correctly emulates a DirectInput device in the control panel (I had to make a copy of an XML file and tweak it to get it recognized, and do the same thing with each game, but I seem to be doing it correctly), though for some reason it thinks there are 4 buttons on it and an extra "throttle" axis which don't actually exist. What's that about?

But then in most games it's either not recognized, or if it is then it won't see all of the axis, or it will mix them up and I have a hell of a time assigning controls (sometimes it will even read multiple axes as the same one so I can't assign them individually), or otherwise when I play a game it will be calibrated all wrong, so that I move very slowly or just keep turning/rolling/spinning very quickly and can't stop. Also, it sometimes seems like it's reading the axes as though it expects them to accelerate my velocity rather than correspond directly to the velocity itself, so that if I let go, I keep moving in the same direction, and then have to push in the opposite direction to slow down or stop completely.

I don't see why it would have these problems, given that ti's just being recognized directly as a normal DirectInput device, like any other, so why wouldn't it work as such, especially since Overload is perfectly capable of using it that way. But even the Descent games and various space flight sims have problems with it!

They look like really weird mice. A lot of games, say some of those you mentioned, were developed at a time where these were not available. It’s understandable that you will have issues. You would need to check the driver and have some sort of interpretation layer. Or just use a normal mouse.
To add, directnput just passes through what it recognises to other software.

I don't think it's a mouse but like the spaceball which was a 6dof controller and something that should have been standard for games at least when descent 3 was out.

Some games are screwed up because of the retarded xinput or xbox controller support.

They're not really normal mice at all, because mice don't have 6 axes, but these do.

And they seem to use the same drivers that they always used all the way back to old devices that used them. And like I said, I know they're DirectInput compatible, because I have mine emulating a joystick and it appears properly in the calibration tool, and is recognized as a joystick in games, but it just doesn't always (or even usually) behave properly.

EDIT: Spectre, I know that some modern games are not DirectInput and only use XInput, but the games I'm testing are all DirectInput compatible (though it's odd that Doom 3 doesn't seem to detect it, considering that I'm pretty sure it predates XInput, but it detects my other controllers).