As a newbie to this game what would really put me off of playing DA after experiencing TOA is the right click ability on techs when trading with other civs.

I can only imagine how difficult it must have been without that ability for players new to DL and DA?

Background story and campaign

Campaign not fully linear (win or replay)

Multiple playable races

Configurable graphics (ie resolution)

Direct planetary intervention is possible (well, actually unavoidable)

Ship designer

Ships are visible in 3D

Battles are visible in 3D

Race typical race behavior

Searches and spreadsheets

Turn based, no fast clicking

Combined interaction with AI players (diplomacy, spying, trade)

Single player challenge

No huge disparity between manual and automatic battles (having no manual )

Somewhat lively atmosphere (from the "funny" technology descriptions to the voice of the street)

(BUTs removed, positive thinking)

As I've noted in the past, the AI personalities that aren't bugged are notably improved from DA.