http://wheelsmfg.com/content/view/477/31/
Check these guys out. No way would I get stuck replacing an entire BB over bad bearings. I still use old cup and cone BB's for that very reason. There is a penalty to be paid in weight, but none of my bikes are feather weights anyways.
Every cartridge BB I have ever had was a disappointment, and I will never go back.
Looks like the Shimano can be rebuilt with a little modification, and in the long run, could save mucho $.