Back in 2005, ACD and I went around a few times about Sergei Schepkin's Goldberg Variations. To my way of thinking, if you're going to take the big anachronistic step of playing Bach on the piano, you might as well go all the way with it. Schepkin is insanely and wonderfully flamboyant, uses the pedal freely, and dresses up every variations with wild embellishments; I love every note. That improvisatory feel does seem very 19th century to me, in the sense that 19th century piano virtuosos were expected to be able to do this kind of thing; listening to some early Chopin on record, you find embellishments there. And, hmm, there are how many 18th c. manuals on embellishments?
Back to Gulda. For anyone looking for off-the-beaten-track Beethoven sonata recordings, take a look at the French pianist Eric Heidsieck, whose EMI complete set used to be available cheap from FNAC (cheap even with shipping to California), Andrew Rangell (on Bridge, and he has a new release out this month), and Ernst Levy (on Marston, if they're not completely sold out). For that matter, I'm in the market for Frederic Lamond. Who he, you ask? A Scottish pianist considered the greatest exponent of the Beethoven piano sonatas in the generation before Schnabel. You can sample him on YouTube, in fact.