There is a small problem with the currently shipping versions of Firebird 2.0.3 for Solaris.
The problem doesn't affect the general workings of Firebird, but if you try to link with the libfbclient library using your own program, you will run into a problem where you will consistently get the following error:
ld: fatal: library -lfbclient: not found
The problem is due to a misnamed libfbclient.so in /opt/firebird/lib
ln -s libfbclient.so.2 libfbclient.so
This has already been corrected in CVS