I've been going to Eurogamer for the past couple of years with uni mates and its quite fun. Not much in the way of adventure games though. I only remember a couple last year - Blue Toad Murder Files; we got to sit and play the first episode and were given woolly hats with the blue toad logo on it and t-shirts which boldly stated "I got lost in Lady Snobbish's bush". Oh and that was where I first played Heavy Rain - I made it crash horribly but it was sooooo good
Its certainly great for all the freebies and was great for meeting some of the companies in person with the careers fair they had upstairs. It gets crazy busy though and you probably will barely see the more popular games (and people are horrible hogs of the consoles). I recommend some of the lectures and talks they have going on throughout the day - they're often fascinating.