Oh man--I didn't like pretty much everything. It reads too obviously like a young writer. He is obviously very conscious in all of his decisions and fails in all of them. His characters are horrible and you don't care about any of them, which usually doesn't bother me except that DFW clearly wants you to empathize with them and care about them. He is way too influenced by Pynchon in the work and his little Pynchonian sidetracks and tangents are completely useless. They add nothing to the story or your understandings of the characters or plot. His parodies of psychoanalysis, psychiatry, education, and pretty much everything else are very heavy-handed and you can almost see him laughing to himself about how clever he is. He tries to create a fully realized, complex world composed of fully realized, complex characters and does neither. Plus, the ending is horrible and unsatisfying. He ties up maybe one of several dozen plotlines which, again, would not be a problem if he didn't structure the work in such a way that he should have wrapped everything (or almost everything) up. All of those things are not done in the way most postmodern work is where it actually adds something to the work. He clearly built up everything and then he was just like, "Well--if I don't do all of these things, everyone will think I'm clever and smart!"
I'm almost done (sorry man--I have a lot of feelings about this book). Finally, the book is transparently structured as a philosophical explication of Wittgenstein's work. I don't know much about Wittgenstein, but after reading some analyses of him and talking to some people who know him, the entire crux of the novel is based on a faulty extension of his thoughts. The idea that reality only exists in what can be said of it is not what Wittgenstein believes and in fact is an illogical conclusion to reach from his thoughts and is something that Wittgenstein himself would have probably railed against. It is simplistically reductionist and, as such, is a weak foundation from which to explore the relationship between reader, author, and text.
Pretty much the only good things are that it is not a difficult novel to get through, so it doesn't take long for its length (I got through with it in maybe 10-12 hours?) and to be honest, you can zone out for sections at a time and miss absolutely nothing.