We are going to develop a large Web application over SAP Portal, most of them in WebDynpro (ABAP). But for some critic functionalities we are going to develop and embedded ActiveX application, that talk with the content page and with the server (via Web Service). We have a little demo of this and its works very well.
But we doubt if ActiveX is a technology with future or not. Honestly we have no experience in .NET and we don't know how develop an equivalent application, as easy to embedded in a BSP, with .NET.