I made some investigation, in 2010, for my company considering PlasticSCM as option. I found some places to improvement which was critical for our company. I made this being in touch with really fantastic, extraordinary and responsive Plastic SCM Support Team.
The problem is missing triggers for push/pull operations. Also internal/external API is not done yet (but You can find some examples of plugins available at PlasticSCM's forum). Without hooks working on central server there is no way to use Plastic SCM in distributed scenario at our company. That is why we choose Git.
Second thing is not missing, but not released support for PostgreSQL. I red on forum You can ask about such ability - and PlasticSCM posses such code somewhere.
PlasticSCM contain so many functions available as plugin and so rich GUI that You want to implement something more "inside". But we still wait for some API to released. I can't wait this.
There is also no floating/enterprise licences and current, "per user", licence model is very expensive. Of course You can contact with sales :)