The joined trait effects many stats, one of them is a 3.3 bonus to warp core.

I made two characters, one joined trill one that was not, both maxed the warp core skill and also had warp theorist trait. The purpose was to see what the extra 3.3 would accomplish.

Result:

Base setting/Control/Joined trill
* denotes a change

Balanced:
50/53/53
50/53/53
50/53/53
50/53/53

Default Attack:
100/100/100
50/53/53
25/32/32
25/32/32

Modified Attack:
100/100/100
*40/44/45
25/32/32
*35/40/41

Conclusion: As I do not know if the game keeps track of actual power levels or simply rounds them, it is impossible to know if there is any bonus using the default power settings. However shifting the base values around to a custom setting it is clear there are some benefits to the power level bonus of this trait even if you take warp theorist and max warp core training.

i'm just wondering where you purchased from as I have yet to receive my retail (purchased from atari).

Atari, they never sent me the code but if you go to the order summary thing (should be a link in the first email they sent you near the bottom) and put in the order number and your password, then click the printer, the printable page it gives you has both preorder and retail code.

For those interested after putting 7 points into Warp Core training I was able to achieve these same numbers. I had the exact same power levels after spending the full 9 points. Sadly I can find no power combination that shows a benefit to spending the two additional points if you are joined trill. Any incremental benefit must be hindered by the +-5 power level slider and rounding adjustments. I would seriously consider not putting those two extra points there if I ever have the option to respec.