its not really flawed apart from the fact it would be VERY difficult to make without a drill press. I would not like to be making one of them
There are easyer methods, but they require a lid to seal it (instead of blockign of channels).
Also a design using a lid instead of cross drilling can perform a lot better becuase the cooling area is concentrated where it is needed.
Heres one of my blocks as an example,
http://server5.uploadit.org/files/kbn2k3-nbbase.JPG all of the pins were made by drilling wiht a 5mm drill, and then I used a cutting disk/ 3mm ball cutting thing, to cut between them. I used an 8mm drill for the space under the inlets and outlets.
Search for rotor waterblocks on google/these forums, they are easy to make and work very well.