Networking is hard, though. People tend to clique with people they already know and it can be tough to break in.
In the past I went to a few Sun User Group and Usenix SAGE conferences. Riveting presentations on things like the switches to cat. The booth babe phenomenon wasn't much in evidence yet.
More recently went to a few OpenStack Summits. Booth babe dress was regulated but they were still there at a fair number of booths. Blew me away that booths would / could actually serve booze.
Did pick up some useful tidbits, but with presentation videos going up on the web eventually one could argue that attendance isn't strictly needed.
What was valuable was getting away from home for a few days, keeping my FFM's from expiring, and meeting a few vendor/community folks in person who I'd only talked to voice / electronically before.
Another dynamic is that within one's company, it can be seen as a negative if one doesn't want to attend conferences, almost like it's required to be seen as keeping fresh, regardless of the cost and inefficiency.
Conferences also have a certain rep for job hunting, and that's another reason I went. Many booths would have "We're hiring!" signs, but when I'd inquire I was brushed off, or told to go to the corporate job site.