My Drobo and the 3 drives I bought from Newegg arrived simultaneously on Wednesday. I had it out of the boxes, installed, and completely functional in under 15 minutes. I put a gigabyte of MP3s on it immediately. I took it home on Thursday night, forgetting the AC power cord in the process, and after a trip back to the office I had a working Drobo connected to my home PC.
Using a combination of SyncToy for the heavy lifting and rsync for accuracy, I began moving my data over. Thursday night, Drobo was at 0% capacity. Today, on a Saturday morning, it's at 67%. At 85% Drobo is programmed to start complaining at you, and above 90% it deliberately limits its throughput in order to nag you into upgrading its capacity.
Basically, this is just a roundabout way for me to say that I bought a 4th drive from Newegg this morning.
I used Junction to create a mount point (an "NTFS reparse point" in Microsoftese) from C:\Downloads to the corresponding Drobo directory. This way, I can drag files from my Desktop to a shortcut to C:\Downloads and have Explorer.exe assume that I mean "move" instead of "copy". By default, dragging a file from your C drive to an E drive would be a copy operation, which in this specific case I don't want to have happen.
So I've moved most (not all) of my data to a little black box no bigger than the little black storage box where I used to keep 5.25" floppy diskettes. And already I'm nervous enough to warrant maxing out the 4 drive bays with another drive.
It's been totally painless, save for a few bullsh*t SyncToy errors that rsync handled like a champ. I have some extra IDE drives laying around that I still need to migrate, and after that I expect my Drobo space consumption rate to level off logistically.