title: Best way to limit a trial version?
body: <p>I'm building a shareware software that allows users to import various types of files (XML, CSV, etc.) into a database. I'd like to provide a trial version, but limit it in some way to prevent users that really need it, from not having to buy it ever.</p>
  
  <p>I considered time based limit, but it seems that there are so many ways to work around that, especially today with virtual machines and stuff.</p>
  
  <p>So, I'm thinking to limit the functionality, but I don't want this trial version to become crippleware.</p>
  
  <p>Have you ever bought some shareware software? What was limitation of its trial version? </p>
  
  <p><strong>edit:</strong> Also, how do you feel about nag-screens as a user?</p>