They're kind of expensive from an advertising point of view and they don't make too many offers from a publisher point of view. As an advertiser you manually select which sites you want your ads to appear on - it will probably be cheaper if you approach the webmaster directly.
My thoughts exactly - the only problem is, you need to know how to negotiate with the website. Because of this, many people find the need to use the "middle man" in order to get quality inbound links.
I agree that text link ads is pretty over priced. I think you will have better results if you find sites and contact them directly.
TLA brings me clients while I am sleeping. So you don't need to promote your links. But link sales forum here at DP is the best place. The problem is that things look so confusing and too competitive for sellers. I think the average prices are getting lower and lower - good for buyers though. I earn about $75/mo. now via TLA. But I don't like to have a broker between You can sell links with good prices if no brokers between you and the buyers. TLA takes too much money, IMO.
I think you were asking about buying links through TLA... As a link purchaser they are expensive - it's far cheaper but more time consuming to seek links yourself (through forums, web searches etc.). I see TLA as a corporate source of links - where the client doesn't mind paying the premium for a middleman.