I've found conventions and conferences to be great fun and definitely worth the expense of attending. I network a great deal online, however -- which means that whenever I've attended a convention, I already know between thirty and fifty people who are there. If you are introverted or just starting out in the industry, I'd recommend teaming up with a group of friends to share a hotel room and explore the conference together. If you're not certain whether you'll enjoy it, I'd also recommend starting small -- with a local convention that doesn't cost as much and won't require a hotel stay.
Some people love conferences, and some people hate them. The only way to find out which kind of person you are is to attend a couple.
