i've been a couple of times.  as big cities go, i'd say it's a little less hectic than others i've been to, but i had a good time.  the beer's great!  and there are around 700 to choose from! :)  and there's some great, reasonably priced food too.  i did go on a bus tour that takes you to all the museums and such, but apart from that i just tried as many of the beers as i could manage.  watch out for Elephant beer, blows your head off!!