PS1 version is OK, controls aren't as good as PC. I forget specifics.
None of the levels have presented me with much of a problem. I've never done them on Hard though, partly because there's no in-level saving. I don't like playing parts of a level over after I lose.
Best performance I've gotten is running it on a VM (even without VM hw accel) specifically Virtual PC. DOSBox is also acceptable. NTVDM (Built-in NT/2K/XP/Vista/7 DOS emulation) is unacceptable, even with tools like VDMSound which attempt to work around limitations in NTVDM (namely, limited sound support).
Emon mentioned DarkXL. It's quite promising so far, but the author has dropped back from quick frequent releases (due to his initial interest in the project) to now a longer development time for the next release (still looks like he's working on it hard though, it has an integrated editor).