Yes, you may be right for your situation. I do not happen to have any system available with PCIe slots in it but would love to toy with a bunch of Parallella boards for a CPU-bound thing or two. So for me this is a more interesting option and I've backed their Kickstarter for that reason.
Established technology tends to persist in the face of new technology. -- G. Blaauw, one of the designers of System 360