In my humble opinion ... rebreather diving is an inherently dangerous activity. In fact, I believe that it is still VERY dangerous in its present form and present stage of evolution (no pun intended) ... much more so than open circuit. However, it is a calculated risk that some of us are willing and able to take. Of course, there are certain things that we can do to reduce the risk, such as adequate initial and continuing training, obsessive equipment maintenance, diving with a buddy (something that many of us do not always do simply because it is impractical). However, don't fool yourself ... it is still VERY dangerous and the associated risks should be carefully weighed by anyone considering take the bubbleless plunge.
In response, you may ask, why then would anyone want to do it if the risks are so high? Well, it is truly an amazing experience that can greatly surpass the experience available to traditional open circuit divers. In addition, those of us that are "techies" often enjoy being on the cutting edge with new technology and overcoming the challenges that often accompany blazing new trails.
In conclusion, take any advice that tends to be on either of the extreme ends of the "deathbox" vs. "perfectly safe" debate with a grain of salt. With that said, if I were to try to quantify the danger level on a scale of 1 to 10 for you, my opinion would be as follows based solely on my own personal experiences:
DANGER LEVEL
1 - driving to work in LA
3 - open circuit non-technical scuba diving
5 - sky diving
7 - rebreather diving
8 - climbing Mt. Everest
10 - blindfolded chainsaw juggling (OK ... I haven't tried this one)
Hope this helps