QtCreator is stable enough and a comfortable IDE, although compile/debug cycles are slower on Windows than with Visual Studio. It doesn't have all the fancy features Visual Studio offers, but after using it for a while I just realized I wasn't missing them. Especially in C++, where Visual Studio doesn't provide source refactoring - they really are pushing C# aren't they? ;)
Visual Studio is certainly a nice IDE, but at the end of the day if you have to pay many licences just for the fancy features (depending on the size of your team), that money could be better spent on other tools.
You will also avoid the trouble of maintaining different project files (Visual Studio on Windows, something else on MacOS and Linux), even if you develop on Windows only, time will come when you will have to compile, test and debug minor issues on the other OS'es.
Eclipse is an alternative, but I haven't checked the stability of Designer on that IDE. You might spend some time on configuring each workstation, and you might have to wait for updates. On the other hand, you benefit from the whole Eclipse environment, which could help if you have other needs. But is that worth the risk?
I would definitely try QtCreator first and try to stick with their environment. If that proves to be a problem, it won't be too late to move to VS later.
Your timing isn't too bad either: you should probably test the 4.6 preview, normally the official release should be soon.