Damn right. As people take money away from the development of LFS they will spoil it for those of us that have taken the effort to buy it. That is a tragedy for the sim, and the community as a whole.
Not just that, but there's the feeling that you have helped the devs make the game ever better for future releases, and also it is showing gratitude to the devs for such an awsome game. That is the reason I bought LFS in the first place after playing the demo, and it is also why I would recommend it to anyone else at all.