No issues making/receiving calls at all. I had one phone call where the conversation was breaking up on both ends, but as the other person was driving through a rather large military base here that's known to kill cell signals I'd chalk it up to that rather than my phone.
I live in a 4G area, but my offices are scattered in 3G and 4G areas. If I'm in the 3G area predominantly on a given day, I switch to CDMA to help conserve the battery. There are times I forget to change back to 4G when getting back to home or one of our offices where I can get 4G. I don't really miss it other than when using data. Have not experienced any data drops beyond a few wifi hiccups here and there.