Good post,however you didn't consult Dell before you had the problem..
Dell compellent tool actually has a "reclaim" tool to get the space back which would have made ALL this hard work unncessary...
So it's a good idea to at least consult the techs that support the product first..
Also you said MOST storage vendors have a problem with reclaiming of space.. that's not true.. I worked on Netapp, and as many complaints that I had with Netapp, I didn't find Netapp lacking in space or configuration problems...
I don't see how you can MOVE a file to a different place on the SAN and NOT have the space reclaimed, you must be doing something weird or didn't setup permissions correctly, which could have also been remedied by a tech support session with Dell.
I think you did all of this on your own, which is fine, good learning opportunity, but if you had invovled Dell you would have found out very quickly where your problem was.
I can guarantee it was NOT a compellent issue, this was a USER configuration issue.