> btw: are there plans to add Hyperthreading support in future Versions
> (1.5.1?) of Firebird?

You should not expect this in an bugfix release as 1.5.1.

Superserver can be used on Hyperthreaded or SMP machines as long as
only one CPU does run the Database server, the other CPU can do other
tasks as e.g. running the Windows-GUI.

Elmar