1.) "The lack of safety-feature" ; The Reo has a collapsable spring fuse. In the event that there is a short resulting in amperage exceeding it, the battery will drop breaking the connection. It works. I had a steel drip tip that went to far down into my RM2, made contact with the postive post that caused a short, and that collapsed the spring. SAFETY!
2.) "Not knowing how low my batteries are" ; I always leave with a fresh battery when going out. I've never had a problem with one lasting the day. You know when to switch out batteries because the vape will drastically decline all of the sudden. But really, most mech users never get to that point. A battery routine is a simple and mindless thing to handle. Also, having one of these is cheap;
http://www.harborfreight.com/7-function-multimeter-98025.html
Just leave it chillin' by your charger. Measure the resistance of your builds with it. Accurately check the voltage of your batteries with it before you head out.
Super_X_Drifter made a nice intro to Reo video, and I post it all the time because it does a pretty good job at explaining the Reo without me typing a book...
There are some people that just don't like the Reo, some people that don't want to be bothered with rebuildables, and some people that cannot afford one; but most anybody who owns one and likes it pretty much ditches everything else they own in short time.
I don't use anything other than my Reos.