I once saw Cust, playing in a Sacramento River Cats game, see 17 pitches over three plate appearances and swing only once.
Also in that post is a link to an analysis of the signing from a fantasy perspective from Rotographs, the fantasy arm of Fangraphs.
If Cust is able to meet the Bill James projections for 2012, he should end up worth roughly .5 WAR, which would place his value around $2-3 million.
Until we know the dollar amount of the contract and what moves the Astros need to make to the 40 man roster to make room for Cust, I'm going to withhold judgement on this deal.
*Edit: So now we know the deal is a non-guaranteed $600k with a club option for 2013. Almost no risk for the Astros. You can find a little info about non-guaranteed deals here.