So.. How low of a system ...will new Spelunky, based on your actual direct experience with it, still run acceptably on?

I have a 10 year old PC and it runs like a dream.

I don't know where they've got the "Intel Core 2 Duo 2.8GHz " from, but my 5 year old laptop (2x2GHZ Centrino 2, 9600m GT, 4GB Ram) runs it, like a hot knife runs through butter ;)

Found my netbook from a few years ago and decided to test it out. The game actually runs pretty smooth, except there is a slight framerate drop during foggy/snowy levels.

Specs are:

2 GB RAM
Radeon HD 6290
C-60 1000 Mhz dual core processor

I've also noticed that the game will sometimes crash on start up but when I try running it again it plays fine with no stability issues save for examining the construction sign to the left of the respawn room.

I've played it on a Intel Core Duo, 4GB RAM and Intel Graphics Family Chipset 4. It ran fine, with some framerate drops on busy levels. Problems may arise in cards with an outdated OpenGL version.

I have a fairly nice laptop that is hamstringed by its awful CPU. Even with a measly 1.8ghz the game runs like my gaming desktop. As was mentioned before, the more busy levels kind of slow down, but its hardly noticeable.

Not that I see those very much. Spelunky for me personally consists of 3 mine/cave levels. :P