My only complaint is that I cannot see an answer to the question:
What, specifically and in detail, was the problem with RMFRP that need to be solved by having a new edition?
The biggest reason is portions of the previous editions of RM was designed, in part, by employees of the previous iterations of ICE and was not usable without their permission, which is unlikely to be granted.
Putting the user hat on, I would liked to have seen more content for RMSS/RMFRP, before a new system. I'm not sure how much quality material was going to be forthcoming on that front however and republishing RMSS books for RMFRP wouldn't have gotten me to buy them. It would need to be new material.
Putting the company hot on (and as stated above), I think a new edition was necessary for a number of reasons. The most problematic being the IP legalities. The second issue being where new content was going to come from, how unique that content was, and who was going to create it (time required by the author and the quality of that authors work).
My primary issue with RMU at this point is, from what I can tell, it isn't near as backwards compatible. It's fairly easy to cross pollinate between the old RM editions, but it seems like that's going to be a larger issue with RMU... which means for someone who is likely to keep using RMSS, RMU becomes even less useful. For example, if round structure and how Haste works has changed, I can no longer use spell lists with Haste on them. Simply using an RMU spell list as is and changing the Haste spells to how they used to work might have balancing implications that I'm not okay with... which means redesigning the spell list entirely, which effectively reduces its usefulness to me. But we have yet to see how this really ended up at the finish line. Odds are good I'm going to pick up most the books for various reasons, but odds are also good (at this point) I may never use them.