I have both a liberated borg captain (lifetime sub) and a borg bridge officer through Amazon. I was able to create the captain on the first day of headstart and it had the abilities that are described under the STO pre-order FAQ page for the borg bridge officer (nanites, efficient, etc).
When I was finally able to get the borg bridge officer today, it was (as several of you have already described) just an engineering officer with skills that seem like you could find on any other engineering officer. I was able to customize it just fine. I too ordered from amazon as 1) it had the lowest price and 2) it seemed like the borg bridge officer would be the best pre-order bonus (in terms of long term use). However, now, it seems like it was purely cosmetic with no differentiation between it and a regular engineering officer.
It really looks like cyrptic is doing their nice little trick of not giving all of the information out. I've loved the game, not too happy with the lack of communication (or lack of accurate communication) from the developer.
Oh well. Do I regret getting my order through amazon? No. Looking at everything else, I still stand by my decision that this was probably one of the better pre-order bonuses to get (joined trill is probably the best but oh well).
On the plus side, it is kind of cool having two borg in my bridge team (captain + officer). Now, if they would only fix the bug of only allowing humans to wear the bonus uniforms...