We're developing/supporting 2 large MFC applications, using VS 2005. Currently, we are looking at various MFC GUI/controls component libraries:
The samples/demos provided for those look all great, and the feature sets seem to match more or less between those libraries.
Parts of BCG have been incorporated into MFC in VS2008, so I assume at least Microsoft likes it.
I know one of our products use BCG, and we haven't had any major problems with it. Then again, I rarely work with UI, so I can't really share any first-hand experience.
You could try Visual C++ 2008 Feature Pack available for Visual Studio 2008. It is official part of Visual Studio powered by BCGSoft.
From personal experience: When the need in using Property Grid control have arisen, I've tried BCGSoft solutions, but it was less convenient than using .NET PropertyGrid (through C++/CLI wrapper).
I used codejock's a couple of years ago. The library was really good, simple to use, good documentation and good, fast support (they even wrote a sample for me to demonstrate what I was asking for.)
I would recommend them, although I have not tried the others you have mentioned.
Toolkit pro seems to be quite popular, id software and Crytek use it for example for their editors. I looked at the BCG once, and the documentation at least was quite bad; didn't have a chance to actually work with the Toolkit pro stuff, but their trial was looking nice.
We're using the new MFC classes from Visual Studio 2008 in a product. Previously we were using BCGControlBar Pro, the conversion to the new MFC classes had to be done by search and replace.
One important thing that BCGControlBar Pro lacks is a resizable layout manager, for this we use a 3rd party codeproject component (which is a pain to use). Codejock has a resizable layout manager.
Another interesting thing that Codejock has is XAML support. Here is their development forum XAML section and (bit dated) XAMLPad like test tool. This would have saved me the time used for creating nice GDI+ gradient buttons (Codejock uses GDI+ for XAML and I had to clone the buttons from a WPF project)
The resizable layout manager and XAML support make "Toolkit Pro" from Codejock a winner in my eyes, even though I haven't used it.
Visual C++ 2008 Feature Pack was included in Visual Studio 2008 SP1. It's not as powerful as BCGControlBar Pro. And it's not for Visual C++ 2005.
Microsoft will provide better official GUI libraries for its Visual C++ and Visual C# products.
I tried both Prof-UIS freeware and BCGControlBar Pro. Prof-UIS is slower than BCGControlBar Pro, but it's easier to use.