Intellisense has been around a really long time. According to Wikipedia:

IntelliSense was first introduced as a feature of a mainstream Microsoft product in 1996, with the Visual Basic 5.0 Control Creation Edition, which was essentially a publicly-available prototype for Visual Basic 5.0. Although initially the primary "test bed" for the technology was the Visual Basic IDE, IntelliSense was quickly incorporated into Visual FoxPro and Visual C++ in the Visual Studio 97 timeframe (one revision after it was first seen in Visual Basic). Because it was based on the introspection capabilities of COM, the Visual Basic versions of IntelliSense were always more robust and complete than the 5.0 and 6.0 (97 and 98 in the Visual Studio naming sequence) versions of Visual C++, which did not have the benefit of being entirely based on COM. These shortcomings (criticized by many VC++ developers since the 97 release) have been largely corrected in the post-.NET product lines. For example, one of the most requested capabilities missing from the pre-.NET products was support for templates, which is now fully implemented.

So that's over a decade. And now, in the March CTP of Orcas, JavaScript joins the club. Jeff King blogs:

The March CTP of Visual Studio marks the debut of a much-requested and long-awaited feature: improved JScript IntelliSense.  We’ve been working on this for almost a year now and I’m pretty excited to finally be able to share it with the public. 

It's actually a much harder problem in a language that doesn't do strong typing.

Kate