I started with the free version, but I think I got tired of the "BUY ME" screen, or perhaps I decided to support the company (I do that sometimes)
Anyway, I don't remember exactly why I bought it. I think I'm entitled to an upgrade... will have to check into it.
100,000 files? Wow. Does the free version have a limit to how many files you can FTP in one session? With the pro version, I don't think uploading 100,000 files would be too different from uploading 100... it'll just take more time. I just select what I need from my drive and click transfer, then I usually go for a walk or read.