The surgery using a robot requires additional incision for placement of the pins.  The operative time is little longer because of this and because of the registration process.
The patient does require a CT scan before the procedure, which involves some radiation.
There is an additional risk in complication (although very low) because of placement of pins into the pelvis.  The pins if placed incorrectly into the pelvis, can damage the structures inside the abdomen and inside the pelvis.
There is also the risk of breakage of pins that can cause retention of hardware or can necessitate additional exposure to remove the broken hardware (if the pin breaks).
The surgeon who is in training and is not very familiar with robotic hip replacement may have significantly increased time in the operating room and the patient can be exposed to increased risk of complications that are associated with increased surgical time.
If the surgeon is not cognizant of the anatomy and the location where components should be placed, the components can actually be placed in an incorrect position.  In computer assisted navigation and robotics, I always say “garbage in and garbage out”.  It is very important to give the robot accurate information.
If the information given to the robot is incorrect, then the robot and the computer will give incorrect information for placement of the implants.  It is therefore critical to have a surgeon experienced not only in hip replacement surgery, but also in the working of the robot when choosing a robotic hip replacement surgery.