Trillian is the most useful if you use it on other devices (I use it on my home computer, my work computer, and a tablet).
The UI might be pretty horrid, but it does what its suppose to, and I never have any lag issues with it.
I've been using it since it was posted on AddictiveTips, and I have to say it is probably the best file manager I've used yet.
I have absolutely no lag, and everything is much more fluid than the other ones I used.