Chebmaster : having developed cross platform code using FPC for a number of years, I've encountered many bugs, usually OS specific. I'd recommend that you build on at least two operating systems - It helps to identify the source of problems, to eliminate common code etc.

I've found FPC 3.0.x to be very stable, my code is working on all the OSes I currently support and it touches everything you'd expect from a modern engine - I had a few issues with 2.6.x.

There may be some issues that were introduced perhaps but don't dismiss it entirely just in case you spend ages trying to get round a bug that was later fixed - which is a more likely scenario.