1. Which software do you use?
Sibelius
2. Do you use it for composing or simply to typesetting
Composing.
3. If you use it for composing, do you find that it helps the creative process?
I have a limited pianist technique and writing directly to sibelius enables me to achieve certain effects which would be impossible otherwise.
4. In what ways does it limit your composing in either the short term or the long term?
I find with Sibelius, writing out out dynamics, tempo, hairpins etc is time consuming and so I tend not to bother, to the detriment of the composition. Also certain instrumental effects are difficult to achieve via sibelius's software (marcato, bartok pizz etc) so I tend to use short term expedients such as converting to midi and running through soundfonts.