I prefer to work with Visual Studio 2008 and .NET for a long list of items that are entirely missing or in my opinion inadequate in Team Developer. However, the most important one is not directly and technically related to Unify's Team Developer. It has little to do with how good TD may be or will ever be and that is:
Developers Community!
When you switch from Team Developer to Visual Studio, as a former Gupta developer, you will feel like a kid in a candy store. Having started to develop in the 80's I felt a bit like a cave-man suddenly catapulted to modernity.
You will astounded by the enormous amount of code, controls, blogs, components, samples and resources that are available to .NET developers.
Just to give a small example, I was looking out of curiosity for a lightweight HTML renderer control. In few minutes I found this: http://htmlrenderer.codeplex.com/
It's free, it's light, and you get the full C# source code.
Nothing can possibly beat the availability of tons of code and the enourmous flexibility and integration that .NET gives to your applications.
Being able to mix together all sorts of components, to interact with all kinds of systems, to draw from an enourmous community of companies and developers, and to run at speeds very close to standard C/C++ code (C# is ultimately compiled to machine code) is something that Gupta developers can achieve only by switching technology.
It doesn't matter how good you may think Team Developer is. The fact is that the IT world is .NET or Java (and the everlasting C/C++). Something new may come up in the future, but I cannot possibly see SAL becoming the programming language of choice anytime soon (or late).