> Also I wasn't a fan of how every client looked like they were straight from XP.
You keep repeating this line. If a FTP client has received heavy usage and development since the XP days, that's a good sign, I think. It proves that it is well used, tested, reliable, and capable.
I'd much rather have a program with a passable UI that is lightweight and does everything I want, than one that has an unjustified resource usage to feature ratio.