> So is there a safe way to use utf-8 with firebird 1.5.3?

UTF8 is an alias for UNICODE_FSS in Firebird 1.5.x. The question is what you
understand under "safe". Jaybird handled UTF-8 in Firebird 1.5.x correctly
and will continue doing so.

> (How about collations in 1.5.x and 2.0?)

There is no collation support in UNICODE_FSS (in other words - only binary)
and three collations in new UTF8 (UTF8, UCS_BASIC and UNICODE).

Probably you want to ask Adriano about collations, since I do not know all
the changes there.

Roman