My daughter will be 18 months old this Saturday, and she isn't only walking, but running, climbing and into EVERYTHING. However, just six weeks ago (16 1/2 mo. old) she still wasn't walking; she seemed to have no interest in it at all!! And like you, it worried me to death!! My husband and I did all of the same things you guys are doing.. She would walk like a PRO with just one pinky finger to hold on to... But the minute you took your hand away, down she went. She would pitch HUGE fits when we would try to get her to walk back and forth between us. We finally decided she would walk when she wanted to walk; she has always been a very strong willed, independent child.
One weekend we were out of town visiting my parents, & the first question my mom asked me was if we had any new walking developments. I, somewhat bitterly, answered no and went to put our bags away. I heard my mom shriek and yell for me.... When I walked out of the room with our bags, our little one proceeded to stand up and walk across the living room and into the kitchen to find me!! She walked so well that my Mom thought we were just trying to surprise her about it!! And since that day, lily has been unstoppable, walking like a pro! She was 16 months and almost 3 weeks old.
With all that said, I don't think you should be too worried :) little ones have a surprisingly strong sense of self and seem to do most everything on their own timeline, not ours. My ped. told us she wasn't the least bit concerned about lily not walking at 16 mo. In fact she told me that many children that are later in physical milestones tend to be early in developmental milestones, and I've noticed this to be true with Lil. He'll walk when he's ready... He won't crawl into his 1st grade classroom :) no worries, mama!!