I can't speak for every single VST or sample pack out on the market - but all of the ones I've used (East West, VSL, Vir2, CineSamples, Sample Modeling, etc) all are C-concert meaning you don't have to transpose them. Rarely have I come across a patch that is sounding a different note from what I'm playing but that usually is an effect and comes with more electronic-based samples (like a few patches in Reason). And in those cases you can usually reset the pitch setting so that it doesn't transpose. But if you're worried about transposing instruments (like trumpets, french horns, saxes, etc) nope - you should be fine.