Edit - attributed this to the wrong source, because I'm a great big idiot. The original story's actually here, and is replete with further details on Mirror's Edge's likely requirements, so well worth a read.
Are game system requirements a valid post? Ooh, it's a toughie. There's nothing more PC than specs - witness the number of Forum-men who display their PCs' fact-innards in their sigs- but they're hardly a mine of wonder to write about. For instance, apparently Mirror's Edge needs a PC something like this:
# CPU: Pentium 4 at 2.4 GHz / Athlon 64 2800+
# RAM: 1GB
# Gfx card: GeForce 6 Series with 256MB VRAM or higher, or ATI X1650 (or HD2400)
Is that interesting? I honestly don't know. Possibly interesting is that my immediate reaction is "oh, that's a fairly low-end system", which either means that I'm a monstrous hardware fascist (more than likely) or that the concept of what a modern gaming PC is has changed somewhat over the last year or so.
I suspect it's a bit of both. My presumption is that a vast majority of Mirror's Edge's potential player base will shrug those specs, and hence this post, off as pretty much irrelevant to their significantly beefier machines, but are there those of you out there who were hoping to play this game on a lesser PC than the listed, and hence crying yourselves to sleep?