If you've ever struggled with converting a vmdk disk format to qemu's qcow format you might have better luck now. One of the projects in last years Google Summer of Code program was to improve support for vmdk within qemu. The outcome of the Summer of Code project has already been merged with upstream qemu so it's available if you pull from git.
The qemu-img binary is responsible for disk management so if you would like to try the latest (unstable) vmdk support you can run the following commands to get it.
$ git clone git://git.qemu.org/qemu.git $ cd qemu $ ./configure $ make qemu-img
You can then use the qemu-img tool for managing your vmdk disk files.
So if you've given up on converting some old vmdk files, give it another try and please post feedback, comments or questions on your successes or failures.