I've been using Lazarus and FPC to port a commercial Delphi game related application to Mac OS X and Linux and it has been relatively painless.

Not everything is working 100% yet, but the same codebase compiles and runs on both Mac OS X and Linux using the LCL and I think we are at about 85% finished.

Lazarus is not perfect, but it is starting to give Delphi a real run for it's money. It annihilates Delphi in the portability stakes, and since it's open source, it will just be a matter of time before it matches Delphi in the userbility stakes.

Take a look, you may be pleasantly surprised.