PSREdit500 was my choice
I just plunked down the $35 for PSREdit500 to control my PSR-600 scanner. I've been trying it out, along with Win500, over the last months to see which feels the most comfortable. PSREdit500 won me over. However, I'm using this WIndows software on Linux under WINE, and I'm doing some wacky stuff with forwarding my scanner's serial connection over my LAN, so I'm kind of a funky type of user.
I really like the smooth RR import functions, the Scanlist management, and the V-Scanner folder and file management. The Monitor function *within* PSREdit500.exe doesn't work for me, but that's okay, as I just use PSRCtrl500.exe to monitor. Do note that it appears that, at least in my funky setup, running both PSREdit500 and PSRCtrl500 at the same time doesn't work so well; I don't think that each program can tell if another is using the same serial connection.
This is totally subjective, but PSREdit seemed to crash less under WINE than Win500, and there are less odd interface flickers/partially painted buttons/interface glitches. I didn't *mind* Win500, mind you, it is just that I had to pick one... It does appear that PSREdit500 gets less chatter here, but I'm thinking that's because it mostly Just Works(tm)?
Good luck.
P.S. ARC was a no-go for me, as the interface glitches were just unbearable under WINE. YMMV.