For me personally, I disliked the pre-iOS 7 version of callbar. I found it too hard to use, it would be small enough to ignore when I'm doing my stuff but when I actually wanted to use callbar, everything was way too small
With this version, I can just hide callbar by swiping up and whenever I need to use it, either tap the status bar or swipe down to open the notification center along with the callbar controls
Doesn't seem to bother me. But one annoying thing I found is that sometimes callbar when you try to unhide the callbar controls by tapping the status bar crashes you to safe mode
I guess another inconvenience with callbar (old and new) in general is that you don't get much information when you got a call waiting or you're trying to call another person while already in one but I don't do multiple user calling at the same time enough to make me uninstall callbar 7. I did consider it at one point though