I've run web browsers alongside heavy cad applications on way lower hardware and not that long ago.
...think my most responsive desktop so far have been a 150mhz 129mb ram Indy pizza box running irix 5 something, driving a 24" crt with considerable more pixel count than fullhd.
Funny thing, back then, The system config whole ui was Mozilla 2.0 engine with js and css1 or something.
The other thing is the hardware accelerated video decoding, watching 1080p h264 with just 10 watts is undeniably impressive.
EDIT: I have reason to believe the sgi pizzaboxes cost somewhat more than $74 as well, even 80s dollars.
Note that there are passively cooled (albeit larger: ITX) Cedar Trail boards available now for about 60% more (total system cost) which outperform this box by a factor of 8x or so, and consume about 30W peak. They have hardware accelerated video too (though the GPU acceleration requires proprietary 32-bit-only drivers).
http://www.amazon.com/dp/B0079VVLZG
I haven't bought one yet, but am eyeing them for my next gadget project. Intel has a family of boards in this price range.
And of course for things that are not graphics, it's a PC, not a no-name ARM SoC. You can run RHEL or Ubuntu on it, plug in your favorite PCI card, etc...
The novelty is the size of these devices. I also run Word and Excel on a 386 at 40 Mhz but it was a full tower not a credit card sized box.
Btw, the pizza boxes were considered incredible small back in early 90s :)
The sgi Indy even had a "portable" version with attached lcd screen.