I also used to think that signal boosters were a waste of money until I bought one of these
Over the past few months I've used it along with my laptop in many locations, and it has always helped. (most of the many reviews state the same).
Apart from boosting the signal from the router I was intending to use, it always shows loads more (many of which are often totally unencrypted), and whilst staying in hotels, I have "borrowed" these open networks to send the odd e-mail or two.