IMO is the best video calling app for smartphones.
before I use to do video chatting using skype but thats in computer. When I started using skype in mobile it gives lots of trouble like hanging etc. etc.
But from last few months I am using this IMO for my video calling I am not facing much issues except when I have week network. If I have 3G network then no one can stop my video chatting or calling.
I strongly recommend this app for the one who uses video calling regularly.