What is the ratio of nicotine in ecigs vs actual cigs?

Extremely variable (ecig juices are available in a variety of strengths), but nicotine alone isn't particularly addictive. Tobacco also contains harmala alkaloids which act as monoamine oxidase-inhibitors in vivo, which potentiate any psychoactive drugs which result in increased serotonin, dopamine, or norepinephrine signaling (like nicotine). It's this synergistic effect that makes tobacco particularly addictive.

There are actually a few e-cig juices which contain all of the psychoactive chemicals as tobacco (known as Whole Tobacco Alkaloid, or WTA juices), and my own experience is that these WTA juices have a substantially different psychoactive effect and are more pleasurable than the rest of the nicotine-only juices. My first few experiences with e-cigs with nicotine-only juices were rather unsuccessful, but I found it much easier to transition off of analog cigarettes by using one of these WTA products, and then was able to transition to nicotine-only juices.

Last I read the biggest potential harm was pneumonia because of the vapor and this was a rare occurrence.

From my research lipoid pneumonia (the form linked to e-cig usage) seems to only have occurred in individuals using e-cig juices which contain oil-based flavorings. Since these few reports surfaced I don't know of any company which still sells juices that use oil-based flavorings - but since it is still a largely unregulated market it is possible they still exist.