If you keep your head on straight, have a focus, and stick to it, they can both be a lot of fun and really useful.
Say you're looking for an artist - the artist's alley has tons of new artists looking to carve a path for themselves.
The panels can help you learn writing, learn new tricks, or even enforce the knowledge that you know what you're doing, and need to develop a %*$& project already!
Nobody is going to walk up to you and offer you a contract or anything, but they can be a great contact tool, learning tool - and you can walk away with free art!