Thanks for the input. Jumping from Delphi to FreePascal/Lazarus shouldn't be too hard - but Pascal's not a language I like too much. I'll look into Lazarus further, though.

D/Vala are both obvious choices for a native language version, but I'm not sure why you says "it['ll] run better". mediaserv doesn't do much which requires CPU power, off-loading all the heavy lifting to mencoder.

The key requirements, therefore, are: maintainability; robustness/reliability; ease of use for end-user.

Native language wins on all three counts to a degree, coming out miles ahead of anything else on the last point.