Depends on what you're doing. RAID 0 is great if you're a very heavy disk user. Take me for example:
I'm usually downloading torrents at 800KB/s, watching a movie, and maybe unrar'ing a tv show all at the same time. With RAID 0 is pretty seamless. Games also load a little bit faster with RAID 0.
However, Windows or programs don't typically launch any faster. Again, it depends on disk usage at the time of program launch.