Not to mention that some of that software is sensitive to which kernel you are using... For instance, for a while I couldn't update the kernel on an RHEL5 serv

Not to mention that some of that software is sensitive to which kernel you are using... For instance, for a while I couldn't update the kernel on an RHEL5 server that I have, because TSM I/O would drop like a rock. I could switch to newer kernels only after I updated TSM to a newer patch level. No idea what would happen if I happened to run TSM on an "unsupported" distribution...