Hi,
uNet is unfortunatly not a good solution for solid projects, the only advantages using uNet is that it works in LAN situations, otherwise, I would strongly advice against, and choose Photon instead.
Be also aware that if you plan on releasing anything to the public using uNet and its matchmaking system, you will need to contact Unity directly.
Also, uNet is a far more complex network system requiring for its main usage a dedicated headless Unity version running on servers, like Amazon, needless to say this is really, really, really expensive
All this to say that PlayMaker support for uNet is limited for the time being and not officially supported, only via the wiki actions I created a while ago for this.
Could you tell us more what you plan on doing with you project and what kind of expectations you have as far as its multi player ability?
Bye,
Jean