Hard to find any bad things to say about Krusader. I've tried numerous file managers - tuxcmd, emelfm2, mc, rox... But I keep coming back to Krusader. First of all, I can't live without the two-panel interface, so that wins all the points there. Also it has every feature I may need and looks really good, unlike most other file managers. Obviously, that comes with a price - slightly bigger system requirements, but anyone who is using KDE should be ready for this anyway. If your system has about 512 MB ram you won't feel it. I remember using it on older machines too and it was still kicking.
Overall, my choice for a file manager. But ultimately everyone has their own tastes in the end and many may prefer the less fancy, but still functional ones.