What are the significant rules differences then that make this one a new edition?
The summary upthread could fit any edition of RQ I've seen. I'm a huge fan of the system - in fact it's my go-to system of choice. But I'm not seeing any changes.
I myself made a change a while back; to percentile the characteristics too, bringing them in line with skills. I also did away with hit points and have a four scale wound system instead. (Light, Medium and Severe Wounds, and kill strikes - with variance depending on the body part hit, and weapons giving a percentile bonus to a percentile damage roll.)
BRP/RQ is better imo than D20 systems because it allows descriptive combat results from rolls (GM's don't need to make up what wound you took - the rolls tell you clearly what happened - not abstract a/c and hp results). It avoids the artificiality of 'character class', or level. You can also build whatever character you can imagine - with no need for books full of new character classes. Also, it's basic concepts are elegantly simple - I rarely have any need to consult rulebooks during play - indeed the basic rules have always been possible to summarise effectively on one side of a sheet of paper. With a few tweaks the system works for just about any setting in my experience.