I don't know what it was, but last year I went to a performance and Schumann finally "clicked" for me. He always bored me, except for a few selected works, but now it's like the complete opposite. Pieces I found to be completely boring are quickly turning into my favorites. It's weird, because even learning and playing his music didn't help before, but now it's like a switch just turned on.
Schumann piano concerto is exquisite. I can't believe I used to find this boring before. It's just so beautiful. The symphonies are great. Love almost all of his piano cycles. Chamber music is excellent; string quartets, piano quartet, piano quintet, violin sonatas...
Hey Thalbergmad if you're still around, sorry man, I've switched over to the dark side.
(Funnily enough, the more I listen to Schumann the more I fall in love with Brahms, despite already liking him for awhile.)