Lots of new ideas since just recently moving to a faster server and doing an interworx to interworx mass import!
During this move I had one site that was almost 100GB just about split 50/50 between web and email that just wouldn't play nice with the import tool. I tried a few times to do this import (just this one by itself to minimize load vs the two at a time it can do) and it failed every time. So what I wound up doing is a structure only mass import to create the SiteWorx account than then doing a remote rsync copy of all the account's files from the old server to the new one. What took hours, more than 6, to do the full import (which failed), I was able to accomplish in about 1 hour or so doing the remote rsync copy.
Keep in mind this was for moving all my sites from one server to another, inside the same datacenter, plus being able to use a LAN connection between the two servers. I know this isn't the case for everyone, so obviously this would be an option, in addition to the default tgz setup...but would be really cool if it was an option.
My Idea
Basically I'm thinking if you have a situation like mine, a direct rsync between the two servers versus creating a tar package, zipping it, then sending it as one big file to the new server can work much better. You would think with the greater overhead of doing file by file versus just moving one big tgz wouldn't make sense, but in my case it actually worked and was at least 6 times faster.
I understand the tgz method makes sense because it is using the already existing backup system that is used through interworx, but I think this special case would make sense for the mass import tool. Create a simple structure backup, move that over, create the siteworx account on new server (just like it does now), then just rsync over all the files.