No issues with new firmware, but I only played on them for 2.5 hours (mind you, live at a show).
For my needs, I've never run my music through Recordbox. Seems like many bugs as a results from folks on the forums. Just one USB HD plugged in to one deck... the other linked. Over 25k songs. If well organized and folders aren't huge, it performs great.
What you do lose is search functionality and wave generation by not using Recordbox. That can be overcome with good organization and anyone who's been mixing for a while remembers a time when you had to mix without wave information.