I ran cinnamon on 11.10 with an atom 330 that I have set up as an htpc. I like the direction it is going but it is definitely more sluggish than gnome shell and unity.
I suspect that with an i5 you wouldn't notice much of a difference though.
The big advantage of gnome shell, gnome fallback and cinnamon is that they scale incredibly well to fit the television screen.
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