I would love to see some good answers here and look forward to them.
Advantages
1. Gas efficiency (which translates to cost savings vs. OC);
2. Provides warm moist gas (keeping you warmer on cold dives);
3. Silence (beneficial in underwater photography, but also enhances the experience of diving);
4. Decompression efficiency (you always have the optimum mixture regardless of depth);
5. Easier to dive in isolated locations (with additional absorbent and relatively small bottles);
Disadvantages
1. Higher cost of additional training;
2. Higher cost of initial equipment and maintenance (sensors);
3. A higher degree of risk in operation;
4. More challenging to operate (this may be deemed to be an advantage or disadvantage, depending upon the diver's preference)