Problems with newer kernels

It has become apparent to me that the Linux kernels in Debian testing and unstable (2.6.2x) have all kinds of problems compared to the one in stable (2.6.18), especially when it comes to working with virtualization. I have been trouble booting newer kernels as guest systems in VirtualBox (bug #434723) and QEMU (and bug #449085). There is some chatter in the Gentoo forums to the same effect. I have also had trouble compiling the host system kernel modules of VMPlayer and VirtualBox with newer kernels. If your job requires regular juggling of virtual machines and operating systems, this creates big problems. Plus my UMTS card stopped working (bug #433750), also confirmed by Gentoo chatter. :) I have also tried to build pure upstream kernels myself, but they have the same problems. So my advice to those running Debian post-stable is to stick to kernel 2.6.18 from stable if you are seeing funny issues.