Outside of the ludicrous limitations on quickbars (which is apparently going away for preferred, but still), artifact gear, hide helmet/unify colors, companion customization, and the like...
...non-subbers not only don't get all the quest rewards and have a credit cap, but they have to pay 25% more at vendors, including commendation vendors. Oh yeah, and non-subbers have their commendations capped.
But I digress. Seeing "This item costs more for non-subscribers" (or whatever the message is) every time I'm buying something from a vendor really makes me feel like BioWare is spitting on me for not subbing.
And that doesn't make me any more inclined to give them money.
Oh, and for the argument that one can buy unlocks from the GTN - that only works if people actually sell the unlocks. The Cartel Shop Items listed on my server is three pages of Cargo Bays put up by one guy (for 400,000 credits, no less).