I'm a huge Dylan fan, and have seen him 15 times or so over the last 12 years. Just to echo what many others have said . . . His reputation as a horrible live performer was earned in the early '90s, but he really found himself sometime around 1995. From 1995-2002, he rarely had an "off" night, which is pretty amazing considering how radically different every show was. Since then, he's been a little more hit-and-miss, partially because his voice is really just a shell of its former shell. (Also, his present band isn't quite as exciting or inventive as Larry Campbell / Charlie Sexton band.) But he is still "on" more often than not, and the Patriot Center show was a great example of that. I went to Frederick, and that was an example of an "off" night (although I didn't think it was as horrible as some of you apparently did).
You just have to know what to expect with Dylan. He is constantly messing with his songs, changing arrangements, melodies, tempos, etc. You are likely not to hear much that you truly recognize. On the other hand, all the tinkering makes you hear things in songs that you hadn't focused on before, at least when he's on.