robot based on Robostix and I2C?

I'm a complete newbie to robotics, so please be kind and use small words. :)
I've just recently discovered Gumstix, makers of tiny little one-board
computers that run Linux, and wondered about their applications to hobby robotics. In particular, there is a "robostix" version which is only $50 (or $40 without connection headers):
http://www.gumstix.com/spexExpnsion.html#robo
This sports an I2C interface, which I also just learned about this week (remember, I'm the newbie). It seems like you could take one of these $50 computers, string together some I2C sensors and motors, program the whole thing in Linux, and have a complete solution that's both cheaper and way more powerful than, say, an RCX brick or Handyboard.
I'm wondering if anybody here has any thoughts about this approach. One concern I have is whether jumping on the I2C bandwagon is going to make for expensive robots -- it seems like all the I2C gadgets I can find are made by Devantech, and those guys aren't cheap.
Their dual motor driver is $102, for example; if I can't do better than that then I'd be better off buying an extra RCX brick for every three motors I want to control. It also seems to a bit over-engineered too, with RC inputs and so on; I wonder if there are cheaper I2C motor controllers elsewhere.
But enough from me... what do y'all think?
Thanks, - Joe
,------------------------------------------------------------------. | Joseph J. Strout Check out the Mac Web Directory: | | snipped-for-privacy@strout.net http://www.macwebdir.com | `------------------------------------------------------------------'
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Note that you can't run linux on the robostix -- that only has an atmega128 on it. You can however hook up a gumstix to the robostix, run linux on the gumstix, and use it to control the robostix, having the robostix then do all the motor controlling, etc. Or you can just write code directly on the atmega128 without linux.
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