All EMTs are regulated by state. If the state recognizes an EMT-I, you can then practice at that level... depending on the agency; a lot of companies don't feel comfortable with a guy they see as having more training as a basic, but less than a paramedic. Liability and insurance also factor in as well-why pay more for a glorified basic (as they see it)when you'll have a paramedic (that you're already paying to do that job). To summarize: you'll get paid as a Basic but be allowed to practice your advanced skills.
As paramedics are to medicine, Intermediates are to pre-hospital providers; you are the red-headed stepchild. Personally, I love having I's around; they make the paramedic's job a lot easier and free up my hands and brain a lot more than any 5 Basics for the very reasons I mentioned above.
National Registry is looking at phasing out the Intermediates (
search here) so, unless there's a specific slot that you are specifically going for (tactical medic on a SWAT team, rescue tech, etc.), go the extra mile and leave yourself that flexibility.
my €.02