VPC is used to run appz that are only and just available in the PC world. However, it is very likely that most people will never ever even touch one of those applications in their dilated computer experience.
The most used programs for the PC are available for the Mac, that is, Microsoft Office, Explorer (and some other independent browsers of magnificent quality), Photoshop, Cubase, Premiere, ACDSee, Realplayer, Flash, Media Player... whatsoever.
Also there are some alternatives to some PC programs, such as RealBASIC to MS Visual Basic, Metro to Cakewalk, Final Cut Pro to Premiere or iMovie to ULead Video Studio, and a long etcetera. So far, these programs are of excellent quality, in many cases better that their counterparts, specially when Apple has been the developer.
An emulator such as VPC is therefore only recommended under certain circumstances that require propietary software, such as an old accounting MS-DOS program you got stuck to, for example. VPC is not recommended for playing, but on the other hand, many good games are ported to the Mac platform so it is silly to try to run them in VPC. Also, old games run very well in VPC, and also in its MS-DOS emulator counterpart DOSBox (dosbox.sourceforge.net).
VPC 6 runs fine in computers with G3 500 MHz processors whenever they have good memory resources (512 is recommended), and a non-abrassive operating system is installed in the virtual hard drive (ie W98). Windows XP is more likely to be installed in computers with at least a G4 1 GHz.