S.W.
I use LinkedIn a lot and have not ever paid the subscription fee. What I have done is increase my connection list to over 500 people, and these are all people who I have actually met, worked with, taught, coached, etc. I also have joined groups - alumni groups from schools I've attended, alumni groups from companies I worked for, and special interest groups in my field. Joining groups increases the number of people whose profiles are visible to you (and your profile is visible to them). Because of the large number of people who I can contact based on a connection, I've not found it necessary to subscribe.
If increasing your connections significantly doesn't seem possible, or you are looking to contact people outside of your current career, you may find that a subscription gives you access to the people you would like to contact. In that case, I think $20/month is a small price to pay for a job search tool.
Another fact - the outplacement company I consult through just completed a survey and found that over 90% of all companies are actively using LinkedIn to find candidates to hire. This is an increase of over 10% from one year ago, when the last survey was done. This doesn't mean just the companies that post job openings on LinkedIn, but companies who search the database for qualified candidates and reach out to them. I've heard from many people that they have gotten calls from recruiters to discuss opportunities purely because their LinkedIn profile looked appealing to these companies.
I highly recommend LinkedIn as a job search tool.