In the facility I work at, (we don't do IV's) the major difference is pay. We do the same work, assesments, treatments, medications, that the RN's do. I insert catheters, administer O2, do respiratory care, do J and G tube care and feeding, do wound care, patient teaching, medication administration, injections, and have even ran a code or two until the paramedics took over. Just like the RN's at my facility.
At the previous place I worked (LTC-geriatric), the RN's did the IV stuff (although I could change primary bags, troubleshoot, and dc lines) and they oversaw the Medicare wing. It was kind of weird actually. It was not unusual to have a LPN be charge nurse when there were RNs on duty. Nobody really cared anyway, we all had a job to do.
In my limited experience in the state of Illinois, there isn't much difference in a LTC setting between RN's and LPN's. Having said that, I am working on getting my ADN. I went for the LPN first because of time constraints. My husband's job had just been shipped out to Mexico (quite literally), I had a two year old who had just been diagnosed with epilepsy, and I needed a good job something like the day before I passed the entrance exam. I plowed through the course (How I earned honors with all the crap going on outside of school is beyond me....), and got a job right out of school. Had I not had so much pressure to get a well paying job, I would have gone the RN route to begin with. More opportunities. I LOVE my job I have now, but I can't see me staying there forever.
There is more of a difference in the hospital setting. Most hospitals around here only employ a handfull of LPN's, prefering RN's because of the broader skill set.
Sorry for the rambling.