I did take notes on the first 30-40 pages. Hampered by the intensely esoteric subject matter and vocabulary, I decided it best to hold off.
I haven't read Vineland though I have heard mixed reviews. The only materials I've read from him: preface to 1984, "Entropy," Crying of Lot 49, and the first chapter of Against the Day. After I finish GR, I had hoped to move on to V.
Recurring themes in his stories/novels: thermodynamics, entropy, Maxwell's demon, Pavlov, anarchism & anarchists, love of another>altruism, altruism>selfishness, fetishism to explain disconnection with love, and women are overwhelmingly empowered especially when interacting with male protagonists (see Katje in GR).
One character that has, despite his roundedness in the novel, has escaped legitimacy after the middle of the second part of the novel is Dr. Pointsman. Although I am waiting for his transformation in the third part as he closely inspects Slothrop's mysterious erection/V-1 rocket connection.