The only disadvantages I could think of are:
- The higher price for clip-less pedals and the need to have cycling specific shoes (which are usually not comfortable in walking)
- Not being able to comfortably ride your bike with normal shoes again. However, you can overcome this by going for dual sided pedals.
On the bright side, you get to use different muscles while pedaling which make cycling more comfortable. You eliminate the chances of your foot slipping off the pedal and getting your leg hit.
When I first started using clip-less pedals, I only fell once. It was because I forgot to un-clip at the end of my ride. Now, if I was going to fall off my bike for any reason, I can smoothly and quickly un-clip my self to prevent the fall.