1) As Rob mentioned, support for the majority of graphics cards including acceleration.
2) A few thousand or tens of thousands of applications that run.
"It sounds like you are asking for a simple veneer over the regular way that a Unix system works"
Very much so, because to solve the needs of RISC OS users, more isn't needed. At the same time they gain all the advantages of UNIX that RISC OS has been missing over the years (PMT, memory protection, multi-user, shared libraries, good development APIs and tools, package management solved)
"whereas ROLF is just trying to use the superior Linux kernel to bring tried and true mechanisms from RISC OS to new hardware."
I suspect ROLF's use of the linux kernel may bring most (all) of the UNIX advantages I listed above, but without applications, it's of less use to end users than RISC OS is.
"At the moment, I'm working on porting NetSurf to run natively"
I presume after you've finished with netsurf, you'll move onto a more capable browser? Because if you've followed any of the endless threads on csa.* you'll know that netsurf, whilst capable hasn't filled all the needs of browser requiring RISC OS users.
You may have created the technically interesting solution, that may in fact be better than the alternatives, but I doubt it's one that will see much use, even inside the former RISC OS community.