The success of House Values leads is entirely up to the abilities of the agent. An agent who expects a free ride will be wasting their money on HV. It is true that some of the leads are just neighbours, or kids, but you can return a lead within 24 hours... so why not call them, or look them up on MPAC to find out if the lead is legit. The truth is that someone was thinking about real estate and that's why they called. Just keep in contact with them, and you will be successful.
I am a new agent and have closed 12 deals in 3 months... I am always on top of the market because I am always getting requests for CMA's either through HV or through my own means. I also have 5 active listings with more in the pipe's.
I am still on the jury with HV though. 1 sale is more than worth it in terms of ROI.

There are always two sides to a story, and remember success doesn't come without some risk.