Just a note, I love using rebreathers and find it so sad when I've got to go back to OC to teach sometimes... They allow you to breath anyway you want, the breathing response is much more "natural" than OC not to mention warm and quite!!
I use the following units: Mk15.5, UT240, Inspiration, Azimuth and Drager Dolphin. I also have been training on rebreathers for over 10 years now.
Unfortunately the product liability insurance (20K/yr) keeps the cost up on the units - but when compared to a high end OC system or a Twin Setup, then Azimuth or Dolphin are only fractionally higher or the same.
I find that most if you travel internationally alot - travelling with the dolphin is the easiest. In fact many places have cylinders and pony available so you travel load it light. If paying an extra $100 doesn't kill you then taking the inspiration is no problem either.
Just my thoughts.