Cool may take the plunge although still in two minds. Played a bit when it was free this weekend but oddly enough I was getting really motion sick with it. Not sure why though but that in itself is putting me off.
Your brain may need time to adjust to the visuals. I sometimes get a little queasy myself when starting a new FPS. You might also want to turn off garbage like Depth of Field and Motion Blur, reduce bloom effects and monitor your frame rate (I bet you all ready do all of this ).
Regarding DLC: I purchased BL3 when it released on Steam but was it was so close to Doom: Eternal's launch that I sort of forgot about it and haven't even finished the main campaign yet! Historically, DLC quality is a mixed bag ranging from exceptional (e.g., Tiny Tina's Assault on Dragon Keep, The Secret Armory of General Knoxx) to exceptionally dull (Claptrap's New Robot Revolution, Captain Scarlett and Her Pirate's Booty). Maybe the overall quality is better this time around (Dave seems to think so) but if you'd prefer to play it safe, DLC tend to be stand-alone experiences and there's nothing wrong with skipping them until you've finished the main campaign. The season pass will inevitably go on sale again this winter.