They all seem to have slightly quirky interface
If you want non japanese screenies of FlexRename I can make some.
That program has far more features than I have ever used
* regexp and wildcard and char-2-char replace
* lots of "pre-canned" renames which are configurable and help you without having to do a regex (dates, cleanup operations like removing "copy n of" or "shortcut to"
* renames based on meta information, iptc, exif, music tags (not ogg yet), office meta tags (MS, not the open office format), html meta tags
* save your options as preset, retrieve them
* all the usual options move-and-rename, copy-and-rename but also delete-what-matches (technically not a rename). change or don't change the date etc.
* files selected by folder, or drag-and-drop to build the list
* add to context menu to run the program or a search from normal explorer use
But mostly I like it because the listing of the files even with subfolders is very fast and so is the preview of whatever transformation you are asking. It feels instantaneous to me. That's the killer feature.
I'm sure many of the other tools in the list have similar features, but once I found this one I kept coming back to it. It's free too.