Programs created with VB are actually a kind of pre compiled source files which uses VB runtime libraries (VBRUN400.DLL, MSVBM50.DLL...etc) as interpreter for execution. These dlls transforms VB functions into one or more windows API calls during run time... this 'execution via interpreter' causes slow... poor performance.

VB is friendly for the programmer... for example.. loading a JPEG file into a screen bitmap, the file I/O operations and the JPEG decoding will be carried out automatically...! But the program will crawl if it is to process those pixels.

VB and all other forms of basic are designed to be able to write a program as fast as possible. If you want efficiency you'll need a real programming language (which one is wisely kept out of the scope of this discussion).
VB is nothing more than qbasic with windows.
However it can be a valuable tool if you want have a prototype of a program ASAP. Or if you need to do a certain calculation several hundred times with different figures (or any other big one-time task), it can be a time saver when you quickly can write a tool to do the job.
And it can be used to teach the basics of software development.

RedX

It's also quite good for creating complex windows and using pre-made ActiveX components. As I've mentioned before, I/we are using VB to create the GUI of one of the leading structural (engineering) analysis programs out there. Despite some VB quirks, it is not too slow to create professional software.

Granted it would be smoother and faster if it were entirely in C, but the software would also be no where near completion now if it were. The tradeoff is (sometimes) well worth it.

- taubz