Commodore,
A couple of issues with importing styles with ObjectDBX: Property sets, Materials and classifications attached to objects do not import cleanly. If a classification exists, it is ignored and a new one is created "myDoocClassification(2)".
I use a different approach which works on everything but classifications. I open the host document via objectdbx and via activex create a block with the object added in question. Then I use objectdbx to import the block into the active drawing. I don't know why this works: perhaps it's because the AEC object was already created. Dunno.
I stopped using classifications for this reason. I haven't checked if this has changed in 2009 - if I get some time I might.
Just thought I'd give you a heads up.