@submicron:
If a company already has a significant investment in Juniper gear, they're going to be fairly skeptical of some candidate who wants to strip it all out for another solution. Its better to learn the gear they have, be proficient with it and then after you've proved yourself to your employer, make appropriate recommendations for how to make improvements. You'll also find that this approach tends to help you plan your pfSense deployments a little better since you already know how the network is configured and can keep an eye out for the little gotchas that any large network retooling project has.
This is a very honest advice. Two thumbs up for this.
@Derek:
"if it ain't broke, don't fix it."
This one I learned in a hard way. ::)