I haven't heard of anyone having a block failure with the CSX block and, from what I understand, a Pond or CSX aluminum block both will require cleanup and certain machining operations to be performed.
There are many threads on the FE Forum about all the blocks, including the CSX block. Keith Craft in the past has said that the CSX head studs add about $800 to the CSX price over its competitors.
Here's just one FE Forum thread for you to review:
http://www.network54.com/Forum/74182...427+Block+info