I have an RPi (with an Atrix dock) that runs RISC OS, and I think it's a beautiful interface, but the problem I have is *doing* something with it.
Case in point, the two computers I probably use 3/4ths of the time are both "vintage" Power Macs (a quad G5, which is my desktop workhorse, and an iMac G4 which is my second workstation). The quad runs the full spectrum of applications, Photoshop, HD video editing, browser (TenFourFox, natch), terminal, software development (mostly in Terminal but a little in Xcode), some games, office apps, and my classic OS 9 apps (QuarkXPress being the major one I need Classic for). The iMac does VNC, terminal, browsing and a little bit of old-school Palm OS development with pluac2. The quad is almost seven years old, the fastest of the Power Macs; the iMac is about a decade old.
Terminal and net access, though, is the majority of what they do and I think the majority of what most people do. I'm fortunate in that I'm skilled and crazy enough to maintain a fork of Firefox for Power Macs (TenFourFox) that can still run on 10.4. We're current with Firefox; our port of Fx20 will come out next week, and we maintain an ESR port for "less adventurous users." Short of plugin support (for security as much as compatibility) and WebGL, the browser supports everything Tier-1 Firefox does, even most add-ons, and even has a PowerPC JIT for JavaScript. This means I don't really need an Intel Mac (I do for Android development and TurboTax, but those are two specific applications).
When I tried using RISC OS on the RPi, NetSurf is very capable within its skill set, but it can't do much, and lacking JavaScript support altogether is a real concern. ISTR there was an Fx2 port at one time, but even our beloved SGIs are now capable of at least Fx3
(not a minor point, since Fx3 is the first Firefox that was Acid2 compliant). And given how important a reasonably current browser is in today's world, it hurts the platform. I certainly couldn't use it on a daily basis, let's put it that way. At least Raspbian has Midori, even if it's WebKit (IIRC).
They recognized this in the PPC Amiga community too. There's at least a Firefox 4 port, anyway, and that's a start. (Various versions of WebKit Origyn still float around on that platform also.)
This is part of the reason I still try to do updates periodically on Classilla, although the renderer is still rather lacking; it can do some JavaScript, and when emulating a mobile user agent, it actually doesn't do too badly on layout. I can take a Mac OS 9 laptop on the road and still do a lot.
Mind you, I don't like putting my money into x86. So, when I needed a laptop that could run Flash for an online course I'm taking (I won't run Flash on Power Macs anymore because of the security pitfalls), I bought a Samsung ARM Chromebook, turned it to dev mode, and installed a miniroot of Arch Linux within ChromeOS. This does everything I need, and I don't need to feed Chipzilla.
Hopefully some enterprising soul in the RISC OS community is trying to narrow the gap. I do like the Iyonix hardware.