The only thing unique the Joined-Trill gets is the trait 'Symbiote' which gives:
+3.3 Starship Energy Weapons , Projectile Weapons , Warp Core Training , Engineering Training
+6.7 Starship Operations Training
I am currently trying to figure out exactly what that means.
In order thats Energy Weapon Damage, Torpedo/mine damage, extra powergrid/energy managment and engineering based ship skills all getting 3.3
Those skills all have the following ingame progression: 6,10,12,14,15,16,17,17.5,18
ie: put 4 skill points in and you have +14 to that skill, so the trill will add 3.3 to that making it +17.3
this will give you a minor improvment to pretty much everything, quite value, adds more value the higher you raise the skill
Starship Operations Training improves practicaly all your sciance skills.
I am unsure if Joined trill will be able to also take the +10 engineering/operations/warpcore traits
okay, so as I understand it...
one of the 4 traits for Joined Trill is an upgrade to 5 skills
like a 500 point skill bonus from go?
Not really... It can't be compared to how much skill points spent due to the diminishing returns of skill points.
As posted earlier, a Joined Trill with 4 Skill points in the various skills with +3.3 is the same as someone with 8 Skill points to the same skill. Roughly. Of course, the Joined Trill can push it further.
What you should really take from this is for those skills they function on a Percent basis. So, it's 3.3% more damage with all energy weapons, and all projectile (torp/mine) weaponry, etc. How it factors in with the Warp Core training is bit trickier though and we're not certain exactly how it is. We do know that a Warp Core Theoriest with level 9 Warp Core Training (18+10) gets +7 to their power settings when they are at 25 power level (aka 32 power level instead of 25).