I also thought so! My grand home automation master plan is indeed to have Meteor running on a Pi, with lots of Espruino's connecting to it.
So I looked into this, and it turns out it's not a problem. Although Meteor isn't officially supported on ARM, essentially it's just a node app, and although people struggled to compile node for ARM in the past, it seems that today there are official binaries for the pi just 2 releases behind (v0.10.24). So looks like we're good!
Incidentally, there is a lot more work in this field than I thought, with Meteor in particular. See e.g. PiJS and enteye, both written in Meteor from what I understand.