I used ProE WF2 at one of my uni internships... I agree with all of the above posts, i will give my experience.
yes, seems to be a little faster, even on slow hardware; this might have something to do with the more regimented work flow.
ProE really shows its unix roots as i think a lot of old code is still there. it uses massive configuration files to set up the cad environment; which can be good or bad, depending if you like editing configuration file (but also allow to easily change configurations though multiple configuration files). if i remember correctly, does not allow for file name spaces, as the old unix file systems couldn't deal with this.
extremely regimented, which may have been fixed, but i was unable to use workflows that seems pretty natural in other cad systems. seems to have a hierarchical assembly system that i found bizarre and a horrible paper environment.
most of my experience has been with inventor, which i still feel is the most intuitive of the packages i have used, although i am starting to like alot of solidworks. Where i reside solidworks is the defacto standard, which really is an asset when it comes to sharing files. if you have to share alot of files, its not always good to be different.