I'm into the sixth chapter of Ulysses. Not as much trouble so far as I feel the book is made out to be. It's a bit more challenging than your average read, but not impossible. I've heard enough about later chapters to know it's going to get more puzzling as it goes on, but quite a fun read so far, I love the mundaneness - details like Bloom eyeing up a woman in the street while his friend is talking to him - and the sheer extent of the inner dialogue of the characters you're privy to.
Now 2/3rds of the way through, only four chapters to go. It's quite ironic that I posted about it in the sixth chapter, as it's in the seventh that the book really starts to go stylistically balmy, sometimes in a good way, sometimes in a not so good way.
The most recent chapter, for example, (Oxen of the Sun) was the most difficult of the book so far. The procession/evolution of styles throughout the chapter is really quite taxing. And yet the last ten pages of it, when the prose has descended into an almost completely incomprehensible chaos, was one of the most astonishing parts of the book so far.
This book has been really amazing overall though. It reminds me a lot of Moby Dick (one of my favourite books), in that both Joyce and Melville are totally flying in the face of the regular way to write a novel because fuck it, I'm telling this story the way I wanna tell it.