I guess two years can make a lot of difference. I used the mcm and 4.5 was not loving it much. I got lots of error windows about missing OB dependencies. 
One of the big problems in installing OB that set me off looking for a different script was the removal of Utilities>>timeStampForMethod: from current images. For older install scripts this absence is a problem. Whoever created the Metacello script for installation appears to have addressed that change. 

Chris