The material quality is class. I know it's for free too and that is possibly attracting a lot of users. My feeling however is that there are many other websites out there charging money and offering a lot less. You should give a load more thought to a subscription based service and/or other ways in which to finance your efforts here. As much as this is a lovely website with fantastic guitar-gen on board; it won't be all that great if it runs out of loot!
PS: I ran a free aviation jobs site for a number of years (sold) and have a good idea how to go about getting the cash-flow up without chasing your users away. Happy to share some knowledge as well as resources if you're interested..?