When using PyQt I know for a fact that the user requires to manually install PyQt, you may supply an installer however that extracts the right files in the site-packages, and install your plugin. This enabled you to have 32-bit / 64-bit Qt embedded in the installer and give users a simple wizard to setup your plugin with all required assets and even environment variables.
If you don't wish to make an installer, you may just add a help file to guide people through installing PyQt themselves.
I have experienced difficulties with Riverbank's own PyQt installer as Maya would give me errors or not recognize PyQt at all, you may wish to try it for yourself though. Otherwise this post will prove useful:
http://nathanhorne.com/?p=460
Maya does have Qt DLLs so I assume compiled C++ Qt using plugins will work on the user end by default - I may be wrong there though for I have not tried it.
Hope this helps you out!