Why spend 20 pounds at ROL online shop for this if RO5 has it for free?
Filer shortcuts & filer thumbnailing are there to have since quite some time by other apps that are free (and run on RO5 too). Submenus no longer obstructing: Freeware offers similar features.
Draw & Paint: It's amazing how important these are taken - I prefer ArtWorks and Photodesk for most work.
64K colour mode: Well, I think whoever decided to do more serious colour work would have a new computer by now, or VirtualPRC or a ViewFinder; and in any case for that kind of work I'd opt for 16M colours!
These are perhaps not enough or well communicated by ROL themselves: Absolutely!
Emulation users do not want RO 3.x since it's too old and has too many restraints I'd say. And since until recently just RO4 was there to have and worked and the emulators emulate old hardware (i.e. RPC) so what's the reason to ask for RO5.
<bold>Under the hood</bold>:
As for the "under the hood work": That's not really an end-user feature, is it, but one of the favorite features ROL promotes is my impression.
Bugs: Well, I assume all RO variants have bugs but from my memory I had more issues when I had Select opposed to RO3 or RO5. And I'd not be surprised that quite a few RO4/6 bugs are side-effects of the changes done to this OS variant and which then have been fixed.
Incompatible RO6: It's incompatible with RO4 and earlier RO6 in some areas. The new screenmode being a more prominent example which some apps need to know of to handle.
Well, zeropage protection is an old one... and there are fixes/tools around!
<bold>RO5 for RPC</bold>:
There are quite a few 3.7 users there mainly due to the simple rule: never change a running system coupled with the upgrade to newer RO versions requiring ROM change and if it is to make sense harddisc reformatting (no tool to convert there). Add to this the information (or lack of such) from ROL about the end-user features (stability fixes are not of any importance to users who's 3.7 system is dead stable!).
Guess what: I had the odd chat with such users and understand their point of view. For me RO4's main benefits were DHCP and long file names. As for further benefits I got from Select ... well ... nothing jumps to my head off head.
Why not give the RPC user the choice: pay for RO4/6 which is the sensible path in case of e.g. podules, or RO 5 (be it 26 or 32 bit) for those just wanting the long file names and DHCP eg.